BIOLOGY CHAPTER 5 IT RUNS IN THE FAMILY
5.1 PASS IT ON
You inherited a lot of characteristics. All your inherited characteristics together is called your
genotype. Some of your inherited characteristics never show. Phenotype= your characteristics
actually expressed. Phenotype= genotype + environmental factors.
Inside every single cell of your body there is a nucleus. This is because the nucleus of the resulting
egg contains characteristics from both parents. Inside the nucleus there are structures called
chromosomes. Inherited characteristics show up as dark bands after a specific staining (figure 5.4).
There are 46 chromosomes inside a fertilised egg. These will copy themselves into 37.2 trillion
chromosomes. All chromosomes grouped up in pairs and in order of decreasing size is called a
karyotype.
Chromosomes are organised in homologous pairs. They match with each other in length and genetic
information. This means there are 23 pairs in each of your cells.
Siblings look similar but almost never identical because there are 2 possibilities of each pair (mother
and father).
People refer to their ancestry as the country or region where their immediate ancestors come from.
(look at pages 124 and 125)
5.2 WHAT ARE THE CHANCES
Chromosomes even determine if you’re a girl or a boy. The last pair of chromosomes in males do not
match. One pair is a pair of sex chromosomes. The other 22 are called autosomes. There are 2 types
of sex chromosomes X and Y. XX= girl XY= boy. Y chromosome is smaller than X. sperm cell= 2 types
Type 1= 22 autosomes + Y = 23 chromosomes
Type 2= 22 autosomes + X = 23 chromosomes
Egg cell= 22 autosomes + X = 23 chromosomes
Girl = type 2 boy = type 1
5.3 DNA AND GENES
DNA= tightly coiled strand of substance, hereditary material in humans and almost every other
organism. Nearly every cell in your body has the same DNA.
DNA is made up of small units called nucleotides. A nucleotide has a base, phosphate and a sugar.
There are 4 types of bases: Guanine (G), adenine (A), thymine (T) and cytosine (C). c and g bond
together and a and t bond together. This is called base-pairing.
The spiral shape of DNA is called a double helix. Your bases form a code. You have 46 chromosomes
in each cell. Each chromosome is filled with many pages of DNA codes.
DNA makes proteins. A section of DNA that has the complete code for a protein is called a gene.
Genes determine the type of protein your body makes.
Proteins are important because they build cells and tissue and can be used as enzymes. Each cell only
reads parts of DNA that it needs to make protein.
5.1 PASS IT ON
You inherited a lot of characteristics. All your inherited characteristics together is called your
genotype. Some of your inherited characteristics never show. Phenotype= your characteristics
actually expressed. Phenotype= genotype + environmental factors.
Inside every single cell of your body there is a nucleus. This is because the nucleus of the resulting
egg contains characteristics from both parents. Inside the nucleus there are structures called
chromosomes. Inherited characteristics show up as dark bands after a specific staining (figure 5.4).
There are 46 chromosomes inside a fertilised egg. These will copy themselves into 37.2 trillion
chromosomes. All chromosomes grouped up in pairs and in order of decreasing size is called a
karyotype.
Chromosomes are organised in homologous pairs. They match with each other in length and genetic
information. This means there are 23 pairs in each of your cells.
Siblings look similar but almost never identical because there are 2 possibilities of each pair (mother
and father).
People refer to their ancestry as the country or region where their immediate ancestors come from.
(look at pages 124 and 125)
5.2 WHAT ARE THE CHANCES
Chromosomes even determine if you’re a girl or a boy. The last pair of chromosomes in males do not
match. One pair is a pair of sex chromosomes. The other 22 are called autosomes. There are 2 types
of sex chromosomes X and Y. XX= girl XY= boy. Y chromosome is smaller than X. sperm cell= 2 types
Type 1= 22 autosomes + Y = 23 chromosomes
Type 2= 22 autosomes + X = 23 chromosomes
Egg cell= 22 autosomes + X = 23 chromosomes
Girl = type 2 boy = type 1
5.3 DNA AND GENES
DNA= tightly coiled strand of substance, hereditary material in humans and almost every other
organism. Nearly every cell in your body has the same DNA.
DNA is made up of small units called nucleotides. A nucleotide has a base, phosphate and a sugar.
There are 4 types of bases: Guanine (G), adenine (A), thymine (T) and cytosine (C). c and g bond
together and a and t bond together. This is called base-pairing.
The spiral shape of DNA is called a double helix. Your bases form a code. You have 46 chromosomes
in each cell. Each chromosome is filled with many pages of DNA codes.
DNA makes proteins. A section of DNA that has the complete code for a protein is called a gene.
Genes determine the type of protein your body makes.
Proteins are important because they build cells and tissue and can be used as enzymes. Each cell only
reads parts of DNA that it needs to make protein.
