Case 1: Gametes in danger?
Learning goals:
1. DNA recap
a. Structure
b. Replication, transcription, translation
c. Repairing mechanisms
d. Mutations (genes)
2. What is mitosis and what is meiosis?
3. What is gametogenesis? Oogenesis? Spermatogenesis?
4. What is the difference in spermatogenesis and oogenesis, when age changes?
LG 1: DNA recap: General information about DNA/RNA/proteins/translation/transcription
DNA (structure, function & replication)
Function:
The DNA stores genetic information and "passes it down" to sustain already existing cells and organisms and to make new ones.
The functional part of DNA is known as "gene", is only 3% of the DNA and the rest is non-coding which means it doesn't translate into proteins
(euchromatin parts have an open structure which can be used for transcription in contrast to heterochromatin parts which have a closed structure that can’t be
used for transcription)
Structure:
DNA is made up of the elements carbon ©, hydrogen (H), oxygen (O), nitrogen (N) and phosphate (P) ( -> combo of phosphorus+oxygen).
DNA has a double helix structure, composed of 2 parallel strands of nucleotides. Each nucleotide is composed of three groups: Phosphate group, 5-carbon sugar /
deoxyribose, Nitrogenous base (A-T: 2 bonds, C-G: 3 bonds).
Two nucleotides are bound together via phosphodiester bond between the 3’-hydroxyl group of one sugar and the 5’-phosphate of the other sugar.
Polynucleotide strands are joined together by hydrogen bonds, maintaining the double helix structure.
DNA consists of:
• Nucleotides, each nucleotide consists of:
○ a sugar (deoxyribose, more specifically -D-2-deoxyribose)
○ a phosphate group
○ a nitrogenous base (hydrophobic)
▪ Purines: A and G - double-ring structures
▪ Pyrimidines: C and T - single-ring structures, U replaces T in RNA
Nucleoside or Nucleotide? -> nomenclature
• Base + sugar = Nucleoside (ex. Adenine becomes adenosine)
• Base + sugar + phosphate = Nucleotide (ex. Adenosine monophosphate AMP)
• DNA Backbone (hydrophilic) -> formed by alternating, sugar and phosphate groups, linked by phosphodiester bonds
Double Helix: 2 strands of DNA wind around each other
○ According to the DNA base pairing rule ->
▪ A pairs with T with 2 hydrogen bonds (break easier)
▪ G pairs with C with 3 hydrogen bonds
Orientation -> the 2 strands run antiparallel (the 3' end lies across the 5' end, 3'-5' and 5'-3')
DNA consist of 2 long strands of nucleotides (antiparallel). The nucleotides of the two strands are connected with each other via hydrogen bonds (2 between A&T
and 3 between C&G). The nucleotides in one strand are connected with each other via phosphodiester linkages between the 3 ’-hydroxyl group of one sugar and the
5’-phosphate of the other sugar group. (3 phosphate groups are attached: 2 phosphate groups (pyrophosphate) + energy is released and 1 phosphor group is used
to connect).
• DNA double helix model of Watson and Crick (3.4 mm is a turn and 0.34 mm between base pairs). DNA is right handed; the thumb represents the helix and the
fingers represent the sugar-phosphate backbone of DNA
• Hydrogen bonds between the base pairs
• Van der Waals interactions in a DNA molecule to stabilize the DNA molecule
• A loop in a DNA structure represent a DNA sequence
BBS 1005-Human Genetics, Reproduction and Prenatal Page 1
, • A loop in a DNA structure represent a DNA sequence
3’-end → has an unlinked -OH group to the 3’position of the sugar ring.
5’- end→ has a free phosphate group to the 5’position of the sugar ring.
Basic Rules of DNA Structure:
• Base Complementarity: A-T (two hydrogen bonds) and G-C (three hydrogen bonds).
• The amount of A equals T (A=T) and the amount of G equals C (G=C), which means A+G = T+C.
• Antiparallel Orientation: The two DNA strands run in opposite directions (5' 3' and 3' 5').
• Double Helix Structure: DNA consists of two polynucleotide chains that are twisted clockwise.
• Sugar-Phosphoric Acid Backbone: The bases are linked by an external backbone, making the structure stable.
This structure is essential for the processes of transcription (DNA to RNA) and translation (RNA to protein).
• Nomenclature
○ Nucleotide (base + sugar + phosphate group) exist of a base (Thymine, Cytosine, Guanine, Adenine in DNA) [1’ C], a phosphate group and a pentose sugar
(2-deoxyribose in DNA) [3’ & 5’] = adenosine monophosphate
○ Pyrimidines: C, T, U and purines: A, G
○ Nucleoside (base + sugar) exist of a (Thymine, Cytosine, Guanine, Adenine in DNA) [1’ C] and pentose sugar (2-deoxyribose in DNA) [3’ & 5’]
○ Nucleotide: adenosine monophosphate – nucleoside: adenosine - base: adenine
Eukaryotes: in chromosomes (p = short arm & q = long arm); exist of two chromatids which are connected via a centrosome (visible in the M-phase: cell dividing
stage). Each chromatid consists of 2 chromatins, which exist of beads (nucleosomes) on a string. Each nucleosome is an octamer which is packed with histones: 2x
H2A, 2xH2B, 2xH3, 2xH4 and 1x H1 (to stabilize) and two times surrounded DNA. The formed nucleosomes are packed with non -histone proteins for a higher level of
compaction.
Chromosomal Packaging: DNA is packed to be protected from mutagens for next generation.
Every cell has: 22 pairs of autosomes (1 from mom and 1 from dad) and 1 pair of sex chromosomes, that makes a total of 46.
Heterochromatin is highly condensed, gene-poor, and transcriptionally silent, whereas euchromatin is less condensed, gene-rich, and more easily transcribed.
Chromosome contain genes: genes = functional units of heredity.
A: Histones and Nucleosomes (10 nm fiber):
Histone octamer → ‘bead’ of 8 histone proteins
Nucleosome: DNA Strand of 147 bp coils around histone octamer.
BBS 1005-Human Genetics, Reproduction and Prenatal Page 2
,B: Chromatin (30nm fiber):
Nucleosomes stack on to each other → coiling of beads present during interphase
C: Looped domains (300 nm fibers: chromatin loops that are anchored to non-histone protein scaffolds
D: Mitotic Chromosomes (700 nm fiber): chromosomes as we know them
Histones
DNA is folded around histones, which are round proteins. If the whole DNA -molecule is around these histones, a chromosome is formed
TYPES OF DNA
There are three different kinds of DNA:
A-DNA (A-form) = right-handed helix, found in dehydrated samples, it is wider and shorter than B-DNA
B-DNA (B-form) = standard DNA double helix in the human body, most common, forms right-handed helix
Z-DNA (Z-form) = left-handed helix, has a "zigzag" pattern, forms with alternating purine-pyrimidine sequences, involved in regulation
Nuclear DNA (nDNA): Located in the cell nucleus, containing the majority of an organism’s genetic code, organized into chromosomes and inherited from both
parents.
Mitochondrial DNA (mtDNA): Found within the mitochondria, this DNA is circular and usually inherited solely from the mother.
Circular vs Linear DNA: Prokaryotes (bacteria) often have circular DNA, while eukaryotes (humans) have linear chromosomes in the nucleus but circular DNA in
their mitochondria.
Supercoiled DNA: DNA that is twisted beyond the double helix, often in a circular form, to fit within cells.
RNA
• Function: conveying information between the nucleus and the ribosomes in the ER, sometimes RNA has catalytic activities, RNA doesn’t store the genetic
information permanent
• Structure: RNA consists of 1 strand with complementary bases in it which bind to each other via hydrogen bonds and fold the RNA into a 3D structure. RNA is
shorter than DNA.
• Nomenclature
○ The bases in RNA are: Uracil (instead of Thymine), Adenine, Guanine, Cytosine
○ The pentose sugar in RNA is: ribose
• Forms:
○ mRNA conveys the information between the nucleus and the ER (Rapidly degraded by nucleases)
○ tRNA is needed in the translation process to read to codon on the mRNA and form the correct amino acid out of it (very stable molecules)
○ rRNA form a ribosomal complex (very stable molecules)
• RNA Poll in compare to DNA Poll:
○ RNA Poll has no exonuclease proofreading because mistakes aren’t passed
○ RNA Poll can start without a primer (TATA box in promoter causes a recognition signal)
DNA replication process: duplicating DNA
DNA replication occurs in preparation for mitosis, when a parent cell divides to produce two genetically identical daughter c ells because each daughter cell contains
the same number of chromosomes as the parent cell, the number of DNA molecules in the parent cell must be doubled before mito sis takes place. DNA replication
occurs during the S phase of the cell cycle (which occurs during interphase, when a cell is not dividing).
- Initiation stage:
BBS 1005-Human Genetics, Reproduction and Prenatal Page 3
, - Initiation stage:
○ Origin of replication is the place at which the DNA helix is first opened (AT rich sequences can be found because less energy is needed to break them open;
eukaryotes have more origins of replication in contrast to prokaryotes which have just one origin of replication)
○ Replication takes place at the replication fork (Y-shape): includes DNA Poll 3
○ Firstly, topoisomerase untwists the helix form of DNA. Helicase unzips the double stranded DNA into two single strands by breaking the hydrogen bonds
between the two strands: especially A&T rich sequences found on the replication fork because there is less energy needed in compare to C&G.
○ SSB (single stranded binding proteins) bind to the single-stranded DNA produced by helicases and they straighten all single-stranded regions
- Elongation stage:
○ Primase adds short RNA fragments to both strands which are a signal for DNA Polymerase 3 to attach (primers: with an OH-group)
▪ Primase + Helicase --> primosome
○ DNA Poll 3 moves as a sliding camp (PCNA: proliferating cell nuclear antigen in eukaryotes) along the both strands and synthesize the new complementary
strand of each template strand by adding nucleotides. Polymerases in eukaryotic cells: α, δ and ε: 5’-3’
▪ Leading strand (replication fork has the same direction as helicase): one primer is needed and it is a continuous process
▪ Lagging strand (replication fork moves in opposite direction to helicase): more primers are needed and it is a discontinuous process. Okazaki
fragments are formed, which are formed discontinuous fragments on the lagging strand. Okazaki fragments are formed, which are formed
discontinuous fragments on the lagging strand.
▪ The new formed DNA strands are semi-conservative
Leading strand: sliding clamp moves in the ‘5 → ‘3, on the lagging strand the opposite (‘5 → ‘3)
- Termination:
○ A sequence causes DNA Polymerase 1 to attach. DNA Poll 1 removes the primer on the leading strand and the different primers on the lagging strand by
switching them into DNA nucleotides.
▪ DNA Poll 1 has exonuclease proofreading, which means that DNA Poll1 checks whether there are no mistakes made in the replication process while it
is synthesizing
▪ DNA poll 1 is only needed once on the leading strand; it is especially important on the lagging strand because of the many primers for the synthesis of
Okazaki-fragments
▪ RNA Hse is used in eukaryotic cells to remove primers: no 5’-3’ exonuclease activity
○ DNA ligase connects the different Okazaki-fragments to one strand
- The replication process is semi-discontinuous because of the difference in synthesizing process on the leading and lagging strand
- The replication process is semi-conservative because of the DNA-templating process (= process in which the template strands are used to form new
complementary strands).
DNA polymerase performs proofreading before a new nucleotide is added to the growing chain.
Exonucleolytic proofreading happens immediately after rare instances that an incorrect nucleotide is added to the growing cha in, it clips in a 3' to 5' direction.
DNA transcription: forming RNA out of DNA
Transcription: Process by which the 3’-5’ DNA strand is used as a template to transcribe/produce an m-RNA molecule. This is why RNA molecules are sometimes
referred to as transcripts. The sequence of RNA strand is complementary to the antisense strand of the DNA from which it is s ynthesized.
- Initiation:
To begin mRNA synthesis, RNA polymerase needs help finding the start site. This is done with the help of cofactors:
○ In eukaryotes, a group of transcription factors perform this role.
Eukaryotes have RNA-poll II that recognizes the promoter (TATA) and binds to it. This is a sign for RNA Poll II to attach to it, forming a transcription initiation
complex.
○ RNA Poll 2 unzips the double stranded DNA. RNA polymerase reads the template in the 3' to 5' direction and builds the new chain in the 5' to 3' direction
○ Eukaryotes have many transcription factors in contrast to prokaryotes which have just RNA Poll holoenzyme
○ The template strand is used
+1 indicates the start point of transcription in this picture. 10 (=-10) base pairs left from the start point it the TATA box → recognition signal for RNA Poll
holoenzyme.
Both prokaryotes and eukaryotes have TATA-like sequences upstream of the transcription start site (e.g., TATA box). Once the RNA polymerase binds to the
BBS 1005-Human Genetics, Reproduction and Prenatal Page 4
Learning goals:
1. DNA recap
a. Structure
b. Replication, transcription, translation
c. Repairing mechanisms
d. Mutations (genes)
2. What is mitosis and what is meiosis?
3. What is gametogenesis? Oogenesis? Spermatogenesis?
4. What is the difference in spermatogenesis and oogenesis, when age changes?
LG 1: DNA recap: General information about DNA/RNA/proteins/translation/transcription
DNA (structure, function & replication)
Function:
The DNA stores genetic information and "passes it down" to sustain already existing cells and organisms and to make new ones.
The functional part of DNA is known as "gene", is only 3% of the DNA and the rest is non-coding which means it doesn't translate into proteins
(euchromatin parts have an open structure which can be used for transcription in contrast to heterochromatin parts which have a closed structure that can’t be
used for transcription)
Structure:
DNA is made up of the elements carbon ©, hydrogen (H), oxygen (O), nitrogen (N) and phosphate (P) ( -> combo of phosphorus+oxygen).
DNA has a double helix structure, composed of 2 parallel strands of nucleotides. Each nucleotide is composed of three groups: Phosphate group, 5-carbon sugar /
deoxyribose, Nitrogenous base (A-T: 2 bonds, C-G: 3 bonds).
Two nucleotides are bound together via phosphodiester bond between the 3’-hydroxyl group of one sugar and the 5’-phosphate of the other sugar.
Polynucleotide strands are joined together by hydrogen bonds, maintaining the double helix structure.
DNA consists of:
• Nucleotides, each nucleotide consists of:
○ a sugar (deoxyribose, more specifically -D-2-deoxyribose)
○ a phosphate group
○ a nitrogenous base (hydrophobic)
▪ Purines: A and G - double-ring structures
▪ Pyrimidines: C and T - single-ring structures, U replaces T in RNA
Nucleoside or Nucleotide? -> nomenclature
• Base + sugar = Nucleoside (ex. Adenine becomes adenosine)
• Base + sugar + phosphate = Nucleotide (ex. Adenosine monophosphate AMP)
• DNA Backbone (hydrophilic) -> formed by alternating, sugar and phosphate groups, linked by phosphodiester bonds
Double Helix: 2 strands of DNA wind around each other
○ According to the DNA base pairing rule ->
▪ A pairs with T with 2 hydrogen bonds (break easier)
▪ G pairs with C with 3 hydrogen bonds
Orientation -> the 2 strands run antiparallel (the 3' end lies across the 5' end, 3'-5' and 5'-3')
DNA consist of 2 long strands of nucleotides (antiparallel). The nucleotides of the two strands are connected with each other via hydrogen bonds (2 between A&T
and 3 between C&G). The nucleotides in one strand are connected with each other via phosphodiester linkages between the 3 ’-hydroxyl group of one sugar and the
5’-phosphate of the other sugar group. (3 phosphate groups are attached: 2 phosphate groups (pyrophosphate) + energy is released and 1 phosphor group is used
to connect).
• DNA double helix model of Watson and Crick (3.4 mm is a turn and 0.34 mm between base pairs). DNA is right handed; the thumb represents the helix and the
fingers represent the sugar-phosphate backbone of DNA
• Hydrogen bonds between the base pairs
• Van der Waals interactions in a DNA molecule to stabilize the DNA molecule
• A loop in a DNA structure represent a DNA sequence
BBS 1005-Human Genetics, Reproduction and Prenatal Page 1
, • A loop in a DNA structure represent a DNA sequence
3’-end → has an unlinked -OH group to the 3’position of the sugar ring.
5’- end→ has a free phosphate group to the 5’position of the sugar ring.
Basic Rules of DNA Structure:
• Base Complementarity: A-T (two hydrogen bonds) and G-C (three hydrogen bonds).
• The amount of A equals T (A=T) and the amount of G equals C (G=C), which means A+G = T+C.
• Antiparallel Orientation: The two DNA strands run in opposite directions (5' 3' and 3' 5').
• Double Helix Structure: DNA consists of two polynucleotide chains that are twisted clockwise.
• Sugar-Phosphoric Acid Backbone: The bases are linked by an external backbone, making the structure stable.
This structure is essential for the processes of transcription (DNA to RNA) and translation (RNA to protein).
• Nomenclature
○ Nucleotide (base + sugar + phosphate group) exist of a base (Thymine, Cytosine, Guanine, Adenine in DNA) [1’ C], a phosphate group and a pentose sugar
(2-deoxyribose in DNA) [3’ & 5’] = adenosine monophosphate
○ Pyrimidines: C, T, U and purines: A, G
○ Nucleoside (base + sugar) exist of a (Thymine, Cytosine, Guanine, Adenine in DNA) [1’ C] and pentose sugar (2-deoxyribose in DNA) [3’ & 5’]
○ Nucleotide: adenosine monophosphate – nucleoside: adenosine - base: adenine
Eukaryotes: in chromosomes (p = short arm & q = long arm); exist of two chromatids which are connected via a centrosome (visible in the M-phase: cell dividing
stage). Each chromatid consists of 2 chromatins, which exist of beads (nucleosomes) on a string. Each nucleosome is an octamer which is packed with histones: 2x
H2A, 2xH2B, 2xH3, 2xH4 and 1x H1 (to stabilize) and two times surrounded DNA. The formed nucleosomes are packed with non -histone proteins for a higher level of
compaction.
Chromosomal Packaging: DNA is packed to be protected from mutagens for next generation.
Every cell has: 22 pairs of autosomes (1 from mom and 1 from dad) and 1 pair of sex chromosomes, that makes a total of 46.
Heterochromatin is highly condensed, gene-poor, and transcriptionally silent, whereas euchromatin is less condensed, gene-rich, and more easily transcribed.
Chromosome contain genes: genes = functional units of heredity.
A: Histones and Nucleosomes (10 nm fiber):
Histone octamer → ‘bead’ of 8 histone proteins
Nucleosome: DNA Strand of 147 bp coils around histone octamer.
BBS 1005-Human Genetics, Reproduction and Prenatal Page 2
,B: Chromatin (30nm fiber):
Nucleosomes stack on to each other → coiling of beads present during interphase
C: Looped domains (300 nm fibers: chromatin loops that are anchored to non-histone protein scaffolds
D: Mitotic Chromosomes (700 nm fiber): chromosomes as we know them
Histones
DNA is folded around histones, which are round proteins. If the whole DNA -molecule is around these histones, a chromosome is formed
TYPES OF DNA
There are three different kinds of DNA:
A-DNA (A-form) = right-handed helix, found in dehydrated samples, it is wider and shorter than B-DNA
B-DNA (B-form) = standard DNA double helix in the human body, most common, forms right-handed helix
Z-DNA (Z-form) = left-handed helix, has a "zigzag" pattern, forms with alternating purine-pyrimidine sequences, involved in regulation
Nuclear DNA (nDNA): Located in the cell nucleus, containing the majority of an organism’s genetic code, organized into chromosomes and inherited from both
parents.
Mitochondrial DNA (mtDNA): Found within the mitochondria, this DNA is circular and usually inherited solely from the mother.
Circular vs Linear DNA: Prokaryotes (bacteria) often have circular DNA, while eukaryotes (humans) have linear chromosomes in the nucleus but circular DNA in
their mitochondria.
Supercoiled DNA: DNA that is twisted beyond the double helix, often in a circular form, to fit within cells.
RNA
• Function: conveying information between the nucleus and the ribosomes in the ER, sometimes RNA has catalytic activities, RNA doesn’t store the genetic
information permanent
• Structure: RNA consists of 1 strand with complementary bases in it which bind to each other via hydrogen bonds and fold the RNA into a 3D structure. RNA is
shorter than DNA.
• Nomenclature
○ The bases in RNA are: Uracil (instead of Thymine), Adenine, Guanine, Cytosine
○ The pentose sugar in RNA is: ribose
• Forms:
○ mRNA conveys the information between the nucleus and the ER (Rapidly degraded by nucleases)
○ tRNA is needed in the translation process to read to codon on the mRNA and form the correct amino acid out of it (very stable molecules)
○ rRNA form a ribosomal complex (very stable molecules)
• RNA Poll in compare to DNA Poll:
○ RNA Poll has no exonuclease proofreading because mistakes aren’t passed
○ RNA Poll can start without a primer (TATA box in promoter causes a recognition signal)
DNA replication process: duplicating DNA
DNA replication occurs in preparation for mitosis, when a parent cell divides to produce two genetically identical daughter c ells because each daughter cell contains
the same number of chromosomes as the parent cell, the number of DNA molecules in the parent cell must be doubled before mito sis takes place. DNA replication
occurs during the S phase of the cell cycle (which occurs during interphase, when a cell is not dividing).
- Initiation stage:
BBS 1005-Human Genetics, Reproduction and Prenatal Page 3
, - Initiation stage:
○ Origin of replication is the place at which the DNA helix is first opened (AT rich sequences can be found because less energy is needed to break them open;
eukaryotes have more origins of replication in contrast to prokaryotes which have just one origin of replication)
○ Replication takes place at the replication fork (Y-shape): includes DNA Poll 3
○ Firstly, topoisomerase untwists the helix form of DNA. Helicase unzips the double stranded DNA into two single strands by breaking the hydrogen bonds
between the two strands: especially A&T rich sequences found on the replication fork because there is less energy needed in compare to C&G.
○ SSB (single stranded binding proteins) bind to the single-stranded DNA produced by helicases and they straighten all single-stranded regions
- Elongation stage:
○ Primase adds short RNA fragments to both strands which are a signal for DNA Polymerase 3 to attach (primers: with an OH-group)
▪ Primase + Helicase --> primosome
○ DNA Poll 3 moves as a sliding camp (PCNA: proliferating cell nuclear antigen in eukaryotes) along the both strands and synthesize the new complementary
strand of each template strand by adding nucleotides. Polymerases in eukaryotic cells: α, δ and ε: 5’-3’
▪ Leading strand (replication fork has the same direction as helicase): one primer is needed and it is a continuous process
▪ Lagging strand (replication fork moves in opposite direction to helicase): more primers are needed and it is a discontinuous process. Okazaki
fragments are formed, which are formed discontinuous fragments on the lagging strand. Okazaki fragments are formed, which are formed
discontinuous fragments on the lagging strand.
▪ The new formed DNA strands are semi-conservative
Leading strand: sliding clamp moves in the ‘5 → ‘3, on the lagging strand the opposite (‘5 → ‘3)
- Termination:
○ A sequence causes DNA Polymerase 1 to attach. DNA Poll 1 removes the primer on the leading strand and the different primers on the lagging strand by
switching them into DNA nucleotides.
▪ DNA Poll 1 has exonuclease proofreading, which means that DNA Poll1 checks whether there are no mistakes made in the replication process while it
is synthesizing
▪ DNA poll 1 is only needed once on the leading strand; it is especially important on the lagging strand because of the many primers for the synthesis of
Okazaki-fragments
▪ RNA Hse is used in eukaryotic cells to remove primers: no 5’-3’ exonuclease activity
○ DNA ligase connects the different Okazaki-fragments to one strand
- The replication process is semi-discontinuous because of the difference in synthesizing process on the leading and lagging strand
- The replication process is semi-conservative because of the DNA-templating process (= process in which the template strands are used to form new
complementary strands).
DNA polymerase performs proofreading before a new nucleotide is added to the growing chain.
Exonucleolytic proofreading happens immediately after rare instances that an incorrect nucleotide is added to the growing cha in, it clips in a 3' to 5' direction.
DNA transcription: forming RNA out of DNA
Transcription: Process by which the 3’-5’ DNA strand is used as a template to transcribe/produce an m-RNA molecule. This is why RNA molecules are sometimes
referred to as transcripts. The sequence of RNA strand is complementary to the antisense strand of the DNA from which it is s ynthesized.
- Initiation:
To begin mRNA synthesis, RNA polymerase needs help finding the start site. This is done with the help of cofactors:
○ In eukaryotes, a group of transcription factors perform this role.
Eukaryotes have RNA-poll II that recognizes the promoter (TATA) and binds to it. This is a sign for RNA Poll II to attach to it, forming a transcription initiation
complex.
○ RNA Poll 2 unzips the double stranded DNA. RNA polymerase reads the template in the 3' to 5' direction and builds the new chain in the 5' to 3' direction
○ Eukaryotes have many transcription factors in contrast to prokaryotes which have just RNA Poll holoenzyme
○ The template strand is used
+1 indicates the start point of transcription in this picture. 10 (=-10) base pairs left from the start point it the TATA box → recognition signal for RNA Poll
holoenzyme.
Both prokaryotes and eukaryotes have TATA-like sequences upstream of the transcription start site (e.g., TATA box). Once the RNA polymerase binds to the
BBS 1005-Human Genetics, Reproduction and Prenatal Page 4
