LS7B Final Review
Exam Best Answers
2024-2025 With 100%
Guaranteed Solutions
Meiosis
Parent Cell: 2 paris of homologous chromosomes (each chromosomes consists of 1 sister
chromatid).
Prophase 1: Crossing over occurs at chiasmata, spindles come out.
Metaphase 1: Chromosomes align at metaphase plate
Anaphase: Homologous chromosomes separated
Telophase 1 and Cytokinesis: 2 haploid (2 chromosomes in each).
Prophase 2: We now have the spindles come out in each cell from meiosis 1.
Metaphase 2: Each chromosome on metaphase plate.
Anaphase 2: Sister chromatids seperate
Telophase 2 and Cytokinesis: 4 haploid cells- each has 2 sister chromatids.
,How is Meiosis similar to mitosis?
Meiosis 2 is similar to mitosis since sister chromatids are separated at both during anaphase (2).
The centromeres split at both processes.
Principle of Segregation
States that allele pairs separate during gamete formation and randomly unite during
fertilization.
Segregation refers to the seperation of homologous chromosomes during anaphase 1!
This was found by Mendel crossing true breeding (homozygous) plants and observing ratios.
Addition Rule
Probability of either event occurring is given by the sum of their probabilities- outcomes being
considered cannot occur at the same time. OR.
Ex. Prob. that pea is round or yellow
Multiplication Rude
Applies when outcomes can happen at the same time and the occurrence of one has no effect
on the likelihood of the other. AND.
Ex. Prob that pea is round and yellow
Principle of Independent Assortment
The segregation of one set of alleles of a gene pair is independent of the segregation of another
set of allele of a different gene pair. Each pair of alleles segregates without affecting or being
affected by the assortment of any other pair of alleles.
This refers to the random alignment of homologs in metaphase 1.
Dihybrid is an example- 9:3:3:1 ratio common.
Epistasis
Genes that modify phenotype expression of other genes. This can modify 9:3:3:1.
For ex. there could be gene that affects pigment population- its a dominant allele that inhibits
color even if animal has genotype supposed to god for pigment! do its II, Ii, or white (ii).
, X Linked Gene and Inheritance Pattern
Genes on X chromosome. Since male only transmits his X chromosome to his daughters and all
male offspring inherit their X chromosome from their mom, CRISS CROSS INHERITANCE takes
place- alternation of X chromosome in successive generations.
An X chromosome present in male in one generation must be transmitted to female in the next,
and in the generation after, its transmitted to the male!!
Crossing Over
Physical exchange of chromosome parts in Prophase 1. Causes recombination of alleles.
Only 2 of the 4 strands in tetrad are involved in crossing over.
Two crossing over events can move everything back into OG place and there would be no
recombination.
Recombinants and Meiosis
After Meiosis, if recombination occurs:
Due to crossing over; there will be two non recombinants and two recombinants (these two
have the two sister chromatids that switched material in tetrad).
Frequency of Recombination
Upper limit is 50% because any new crossover has two equally likely consequences: change a
previously recombinant chromatid into non-recombinant or turn a previously non-recombinant
chromatid into a recombinant.
Use this as measure of genetic distance between 2 genes on chromosome.
(amount of recombinants)/(total offspring) x 100.
In a question, look for the ones that dont have same first genotype as the given... those two are
the recombinants...
Y-linked genes
Located on Y chromosome.
1) Only males are affected
2) Females never inherit or transmit
Exam Best Answers
2024-2025 With 100%
Guaranteed Solutions
Meiosis
Parent Cell: 2 paris of homologous chromosomes (each chromosomes consists of 1 sister
chromatid).
Prophase 1: Crossing over occurs at chiasmata, spindles come out.
Metaphase 1: Chromosomes align at metaphase plate
Anaphase: Homologous chromosomes separated
Telophase 1 and Cytokinesis: 2 haploid (2 chromosomes in each).
Prophase 2: We now have the spindles come out in each cell from meiosis 1.
Metaphase 2: Each chromosome on metaphase plate.
Anaphase 2: Sister chromatids seperate
Telophase 2 and Cytokinesis: 4 haploid cells- each has 2 sister chromatids.
,How is Meiosis similar to mitosis?
Meiosis 2 is similar to mitosis since sister chromatids are separated at both during anaphase (2).
The centromeres split at both processes.
Principle of Segregation
States that allele pairs separate during gamete formation and randomly unite during
fertilization.
Segregation refers to the seperation of homologous chromosomes during anaphase 1!
This was found by Mendel crossing true breeding (homozygous) plants and observing ratios.
Addition Rule
Probability of either event occurring is given by the sum of their probabilities- outcomes being
considered cannot occur at the same time. OR.
Ex. Prob. that pea is round or yellow
Multiplication Rude
Applies when outcomes can happen at the same time and the occurrence of one has no effect
on the likelihood of the other. AND.
Ex. Prob that pea is round and yellow
Principle of Independent Assortment
The segregation of one set of alleles of a gene pair is independent of the segregation of another
set of allele of a different gene pair. Each pair of alleles segregates without affecting or being
affected by the assortment of any other pair of alleles.
This refers to the random alignment of homologs in metaphase 1.
Dihybrid is an example- 9:3:3:1 ratio common.
Epistasis
Genes that modify phenotype expression of other genes. This can modify 9:3:3:1.
For ex. there could be gene that affects pigment population- its a dominant allele that inhibits
color even if animal has genotype supposed to god for pigment! do its II, Ii, or white (ii).
, X Linked Gene and Inheritance Pattern
Genes on X chromosome. Since male only transmits his X chromosome to his daughters and all
male offspring inherit their X chromosome from their mom, CRISS CROSS INHERITANCE takes
place- alternation of X chromosome in successive generations.
An X chromosome present in male in one generation must be transmitted to female in the next,
and in the generation after, its transmitted to the male!!
Crossing Over
Physical exchange of chromosome parts in Prophase 1. Causes recombination of alleles.
Only 2 of the 4 strands in tetrad are involved in crossing over.
Two crossing over events can move everything back into OG place and there would be no
recombination.
Recombinants and Meiosis
After Meiosis, if recombination occurs:
Due to crossing over; there will be two non recombinants and two recombinants (these two
have the two sister chromatids that switched material in tetrad).
Frequency of Recombination
Upper limit is 50% because any new crossover has two equally likely consequences: change a
previously recombinant chromatid into non-recombinant or turn a previously non-recombinant
chromatid into a recombinant.
Use this as measure of genetic distance between 2 genes on chromosome.
(amount of recombinants)/(total offspring) x 100.
In a question, look for the ones that dont have same first genotype as the given... those two are
the recombinants...
Y-linked genes
Located on Y chromosome.
1) Only males are affected
2) Females never inherit or transmit
