Chromosomal Genetics

Question 1

What is the chromosome theory of inheritance?

Answer 1

Genes have specific locations on chromosomes

Question 2

What did Thomas Hunt Morgan work on? (early 1900s)

Answer 2

Fruit flys.

Question 2

What does W+ mean?

Answer 2

Wildtype (the phenotype most commonly found in nature)

Question 3

What does W mean?

Answer 3

Mutant (variation from the wildtype)

Question 3

Do bees and ants have sex chromosomes?

Answer 3

No. Females are diploid and males are haploid

Question 4

What did Morgan conclude when he bred the F1 female wildtype and an F1 wildtype male resulting in a 3:1 ratio with no females having white eyes?

Answer 4

Eye colour is a sex-linked trait

Question 5

Hemizygous

Answer 5

Having only one copy of a gene or chromosome segment instead of the usual two

Question 6

If the genes are on the X-chromosome only, they are_______?

Answer 6

X-linked

Question 7

If the genes are on the Y chromosome only, they are______?

Answer 7

Y-linked

Question 8

What is a barr body?

Answer 8

An inavtivated X chromosome in females

Question 9

Barr bodies are reactivated in____?

Answer 9

Ovarian cells

Question 10

Do females have two functioning X chromosomes?

Answer 10

No. Only one.

Question 11

Is it random which X chromosome gets deactivated?

Answer 11

Yes, it results in genetic mosaics

Question 12

Are tortoiseshell cats usually female?

Answer 12

Yes, because the pattern is related to both X chromosomes

Question 13

Linked genes

Answer 13

Genes near each other on the same chromosome

Question 14

If genes are separated, will crossovers occur?

Answer 14

Yes

Question 15

What are map units?

Answer 15

The number of recombinant chromosomes

Question 16

In Morgan’s experiment, why weren’t the flys perfectly linked?

Answer 16

Because there were recombinants present due to crossing over between the two genes in the F1 female

Question 17

How to calculate recombination frequency?

Answer 17

Recombinants/Total # offspring

Question 18

What is the difference between a genetic map and a linkage map?

Answer 18

A genetic map allows us to see the order of genes and which ones are on the same chromosomes

A linkage map is based on recombinant frequency (how far apart genes are)

Question 19

When does nondisjunction occur?

Answer 19

Anaphase l, ll, or after fertilization (the diploid cell can have an extra copy of a chromosome = trisomy) (only having one copy = monosomy

Question 20

What is trisomy?

Answer 20

Having an extra set of chromosome 21 chromosomes

Question 21

What is the genotype of klinefelter syndrome?

Answer 21

XXY

Question 22

What is the genotype of Jacobs syndrome?

Answer 22

XXYY

Question 23

What is the genotype of Triple X syndrome?

Answer 23

X0 or XX(partial)

Question 24

What does a deletion do?

Answer 24

Removes a chromosomal segment

Question 25

What does duplication do?

Answer 25

Repeats a segment

Question 26

What does inversion do?

Answer 26

Reverses a segment

Question 27

What does a translocation do?

Answer 27

Moves a segment from one chromosome to a non homologous chromosome

Question 28

Which organelles genes are maternally inherited?

Answer 28

Mitochondrial and Chloroplast