Chapter 13

Question 1

Sex-linked (X-linked)

Answer 1

trait determined by a gene on X chromosome

Question 2

What species did Thomas Morgan Hunt look into?

Answer 2

Drosophilia

Question 3

Autosomes

Answer 3

any eukaryotic chromosomes not a sex chromosomes

Question 4

What is the default sex in embryonic development?

Answer 4

Female

Question 5

Genes on Y chromosome

Answer 5

Make male genitalia
Make secondary sexual structures

Question 6

Any individual with one Y chromosome is normally

Answer 6

Male

Question 7

Name an example of a human genetic disorder that is sex-linked?

Answer 7

Hemophilia

Question 8

Which statement is true about inheritance of hemophilia between females and males

Answer 8

Heterozygous females are asymptomatic carriers

Men who receive a recessive allele on their X c’some have the disease

Question 9

Barr body

Answer 9

Inactivated X chromosome

Question 10

Dosage compensation

Answer 10

A phenomenon by which expression of genes carried on sex chromosomes is kept the same in males and females, despite a different number of sex chromosomes

Question 11

Genetic mosaics

Answer 11

When a woman is heterozygous for a sex linked gene, some cells will express the dominant allele and other may express the recessive

Question 12

Nondisjunction

Answer 12

failure of homologues to separate properly during meiosis

Question 13

What are the possible aneuploidies when nondisjunction occurs in female meiosis?

Answer 13

XX or no X chromosomes (O)

Question 14

What are the possible aneuploidies when nondisjunction occurs in male meiosis?

Answer 14

XY, YY, or no sex chromosomes (O)

Question 15

Aneuploidy

Answer 15

gain or loss of a chromosomes

Question 16

T or F: nondisjunction only occurs in sex chromosomes

Answer 16

F: nondisjunction occurs in both autosomes and sex chromosomes

Question 17

Aneuploidy is a result of _________

Answer 17

Nondisjunction

Question 18

Monosomy

Answer 18

loss of one copy of an autosome

Question 19

Trisomy

Answer 19

gain of an extra autosome

Question 20

Down syndrome

Answer 20

an extra copy (trisomy) on chromosome 21

Question 21

T or F: Aneuploidy is more severe in sex chromosomes than in autosomes

Answer 21

F: It is LESS severe than in autosomes

Question 22

Triple X (XXX)

Answer 22

develop as normal females with 2 Barr bodies

1/1000 females

Question 23

Klinefelter syndrome (XXY)

Answer 23

develop as a male with many female characteristics, often mentally delayed

1/1000 male births

Question 24

Turner syndrome (XO)

Answer 24

sterile female, stunted sexual development
1/5000 female births

Question 25

Which aneuploidy variation is lethal during embryonic development?

Answer 25

YO

Question 26

Generally what is the Chromosomal theory of inheritance? And how did Morgan's early work find support for it?

Answer 26

Chromosomal theory of inheritance - theory stating hereditary traits are carried on chromosomes Morgan found

Question 27

How is sex determined in humans?

Answer 27

Sex chromosomes Females: XX Males: XY

Question 28

How many autosomes do humans have? How many sex chromosomes?

Answer 28

Autosomes - 22 pairs Sex chromosomes - 23rd pair

Question 29

Which chromosomes determines 'maleness' in humans?

Answer 29

Y

Question 30

If females have double the X-genes, do they express twice as many proteins encode on the X c’somes? Why or why not.

Answer 30

No, because of dosage compensation, which

Question 31

True or false: Early in embryonic development in females, one X-chromosome gets turned off (Barr body) all cells in the adult female have the same X-chromosome inactivated.

Answer 31

True

Question 32

Why do genetic mosaics form?

Question 33

Nondisjunction of chromosomes in meiosis leads to ___________. (one word)

Answer 33

Aneuploidy

Question 34

Down syndrome is an example of what type of chromosomal disorder?

Answer 34

Trisomy

Question 35

Why would Aneuploidy in sex chromosomes is less severe than in autosomes?

Answer 35

Autosomes is densely packed with genes E.g., if you lose chromosome 1, you will lose a lot of important genes If you are missing a sex chromosome, more flexibility Sex chromosomes have fewer genes essential for functioning What you lost from a sex chromosomes is not as impairing as what you lost from an autosome

Question 36

What types of disorders can result from Aneuploidy of sex chromosomes?

Answer 36

Triple X (XXX) Klinefelter syndrome (XXY) XO OY XYY (Jacob syndrome)