Chromosomal Inheritance I

Question 1

Diversity of Sex Determination Systems

Answer 1

• X-Y System
• X-0 system
• Z-W system
• The haplo-diploid system

Question 2

X Inactivation in Female Mammals

Answer 2

In females, one of the two X chromosomes in each cell is randomly inactivated during embryonic development

Question 3

How do genes on different chromosomes assort?

Answer 3

Unlinked genes assort independently

Question 4

What are the two types of offspring?

Answer 4

Parental-type and recombinant

Question 5

What are the chances of recombination for any two genes on different chromosomes?

Answer 5

50% frequency of recombination

Question 6

What are the chances of recombination for any two genes that are perfectly linked on a chromosome?

Answer 6

0% frequency of recombination

Question 7

Fly Example shows what?

Answer 7

Incomplete linkage, but the two genes are on the same chromosome

Question 8

Why was there recombinant offspring if both traits are on the same gene (fly example)?

Answer 8

Crossing over of homologous chromosomes in meiosis I

Question 9

Recombination Frequency Equation

Answer 9

recombinants/total offspring

Measure of the distance between genes

Question 10

What did Alfred Sturtevant do

Answer 10

Realized that the recombination frequency provided a way to construct the genetic map (the order off genes on chromosomes)

Question 11

What does a higher recombinant frequency % mean

Answer 11

the higher the frequency of recombination between two genes, the more genetically distant the genes are from each other

Question 12

How to calculate distances between pairs of loci?

Answer 12

1 map unit= 1% recombination = 1 centiMorgan

Question 13

Why is the 17% frequency slightly less than b-cn +cn-vg?

Answer 13

Recombination frequency = genetic distance holds true only for short distances
This means that genetic distances can be much larger than the recombination frequency if the loci are farther apart

Question 14

Genetic Map of Fruit Flu

Answer 14

Four linage groups were found. and it was determined that the fly had four pairs of chromosomes

Question 15

Why is the linear order of genes is identical between physical and genetic maps, but the spacing of genes is not?

Answer 15

Physical map: a graphical representation of physical locations of landmarks or markers within a chromosome or genome. Measured in nucleotide bases
Genetic map is measured in centimorgans

Question 16

Why do linked genes tend to be inherited togther

Answer 16

Because they are near each other on the same chromosome. Linkage is the mechanistic basis of how we discover genes that cause diseases

Question 17

What is GWAS?

Answer 17

experimental design used to detect associations between genetic variants and traits in samples from populations

Question 18

How is GWAS and genetic linkage related?

Answer 18

GWAS rely on genetic linkage between genetic markers (like SNPs) and disease associated alleles.

Question 19

Genetic architecture of a trait

Answer 19

the joint distribution of effect sizes and allele frequencies of variants in loci contributing to the trait

Question 20

How are polymorphisms used with genes

Answer 20

For all complex traits, polymorphisms in many genes contribute to genetic variation in the population
For complex traits, widespread pleiotropy is common

Question 21

Missing heritability problem

Answer 21

alleles identified by GWAS to determine height only explain 20% while it should be 80%