Origins of Genetic Variation

Question 1

Three origins of genetic variation?

Answer 1

Independent Assortment
Crossing Over
Random Fertilization

Question 2

How tetrads land on the metaphase I plate =

Answer 2

Independent Assortment

Question 3

Exchange of genetic material between non-sister chromatids

Answer 3

Crossing Over

Question 4

One in 8 million chance?

Answer 4

Random Fertilization

Question 5

Number over permeations possible in humans? Independent Assortment.

Answer 5

2 to the 23

Over 8 million permeations

Question 6

This happens in Prophase I and includes recombination of DNA & exchange of DNA between non-sister chromatids.

Answer 6

Crossing Over!

Question 7

Crossing over happens in…

Answer 7

Prophase I

Question 8

First step of crossing over?

Answer 8

2 Homologous chromosomes align & synapsis

Question 9

During synapsis…

Answer 9

All genes lined up & every gene perfectly aligned

Question 10

This is thought to be the point where two homologous non-sister chromatids exchange genetic material during chromosomal crossover

Answer 10

Chiasma

Question 11

Where the chormatids cross exists an ______/_____ ________ which will ___ each chromatid and _______ __.

Answer 11

Enzyme/Protein Complex
Cut
Reattach It

Question 12

Typically there are this many crossover events on each homologous pair.

Answer 12

4-5

Question 13

Once exchange happens ________ belong to the other & vice-versa.

Answer 13

Alleles

Question 14

Random fertilization ratio?

Answer 14

1:64 trillion

Question 15

Is random fertilization true in other species?

Answer 15

No - in species with promiscuous females there is a competition between soldier sperm!

Question 16

Problems with Meiosis arise in what phase?

Answer 16

ANAPHASE - MI or MII

Question 17

Seperation in Meiosis is called…

Answer 17

Disjunction

Question 18

Abnormal seperation?

Answer 18

Non-disjunction

Question 19

In non-disjunction the daughter cells can be:

Answer 19

N+1 or

N-1

Question 20

When N+1 egg fertilizes with an N sperm we get a zygote with:

Answer 20

Trisomy! 3 Copies of 1 chromosome

Question 21

T/F In humans, Trisomy conditions exist for every chromosome.

Answer 21

TRUE

Question 22

Trisomy 21 =

Answer 22

Down Syndrome

Question 23

T/F Trisomy can’t exist in sex chromosomes.

Answer 23

FALSE - Can

Question 24

If we have a fertilization with an N-1 egg?

Answer 24

Monosomy