Lecture 5

Question 1

What is a barr body?

Answer 1

present inside nucleus of female somatic cells

Question 2

Where are centrioles?

Answer 2

In the centrosomes present outside the nucleus of cells

Question 3

How can you identify a red blood cell?

Answer 3

doesn’t have a nucleus

Question 4

define x-inactivation

Answer 4

one x chromosome does not uncoil into a chromatin– referred to as a barr body – genes are not active on barr body because it does not uncoil

Question 5

do males have barr bodies?

Answer 5

NO- only one per somatic cell in females

Question 6

define barr body

Answer 6

condensed, inacive c-chromosome found in the nuclei of somatic cells of females

Question 7

Who discovered barr body?

Answer 7

Murray Barr

Question 8

How do X and Y chromosomes differ?

Answer 8

differ in size and the information they carry

Question 9

defective genes found on the sex chromosomes are referred to as…?

Answer 9

sex-linked genetic disorders/diseases

Question 10

Which type of sex linked disease is most common?

Answer 10

x-linked recessive

Question 11

types of x-linked recessive disorders?

Answer 11

Hemophilia A, Red-green color blindness, duchene muscular dystrophy, male pattern baldness

Question 12

Who will have x linked recessive diseases

Answer 12

males because women have two x’s so other will protect them- men only have one x so if they have it, they will show it- women only carriers

Question 13

Define Hemophilia

Answer 13

A person with hemophilia is lacking certain proteins that are necessary for normal blood clotting

Question 14

Typical example of x linked recessive?

Answer 14

hemophilia

Question 15

How common is x-linked dominance?

Answer 15

very rare

Question 16

What is the percent chance of a woman with an x-linked dominant disorder passing it to their fetus?

Answer 16

50%

Question 17

Examples of x-linked dominant disorders

Answer 17

vitamin D resistant Rickets, incontinentia pigmenti

Question 18

Are male or female viable offspring due to incontinentia pigmenti?

Answer 18

female offspring- male offspring are mostly not viable

Question 19

Who transmits y linked disorders?

Answer 19

transmitted from father to son- NOT TO DAUGHTERS

Question 20

Why are there few Y linked disorders?

Answer 20

Because the y chromosomes is relatively small and contains few genes

Question 21

Examples of y linked disorders

Answer 21

male infertility, hypertrichosis pinnae (hair in ears)

Question 22

How is mitochondrial inheritance passed?

Answer 22

through genes present in mitochondria - mother to all offspring

Question 23

Example of a disease transmitted through the mitochondria

Answer 23

Leber’s hereditary optic neuropathy- loss of central vision before the age of 30

Question 24

polygenic inheritance

Answer 24

There is more than one gene responsible for a trait- multiple genes responsible

Question 25

What does polygenic inheritance result in?

Answer 25

continuous variation

Question 26

Example of a polygenic inheritance gene

Answer 26

height- result of the involvement of more than one gene | skin color is another example

Question 27

Linked genes

Answer 27

located on the same chromosome and cannot segregate independently because physically connected (close to each other)

Question 28

When is crossing over more likely?

Answer 28

the farther the genes are away from each other on the chromosomeE

Question 29

Example of linked genes in flies

Answer 29

the genes for eye color and wing length are on the same chromosome so they are inherited together

Question 30

Example of linked genes in humans

Answer 30

dark hair and brown eyes, black hair and curly hair, blonde hair and fair skin, dark skin and dark hair

Question 31

Mosaicism

Answer 31

denotes the presence of two populations of cells with different genotypes in one individual who has developed from a single fertilized egg

Question 32

How are cells expressed in mosaicism

Answer 32

cells within the same person having different genetic makeup

Question 33

What causes mosaicism

Answer 33

caused by error in cell division very early in the development of embryo

Question 34

Example of mosaicism

Answer 34

Neurofibromatosis type 1

Question 35

Which cells does somatic mosaicism occur in

Answer 35

somatic - NOT SEX CELLS

Question 36

Chimera

Answer 36

animals that has two or more different populations of genetically distinct cells that originated in different zygotes

Question 37

What is chimera formed from?

Answer 37

four parent cells- two fertilized eggs or early embryos fused together

Question 38

define epistasis

Answer 38

interaction of non allelic genes- one gene affects the phenotypic expression of a second gene

Question 39

Example of epistasis in mice

Answer 39

in mice there is a gene that codes for the presence or absence of pigmentation in fur- the second gene codes for color of fur

Question 40

define pleiotrophy

Answer 40

occurs when a gene has more than one phenotypic expression

Question 41

example of pleiotrophy

Answer 41

sickle cell anemia- gene that codes for hemoglobin is defective- can't produce normal hemoglobin and shape of hemoglobin affected

Question 42

multifactorial and polygenic disorders

Answer 42

cancers, diabetes, heart disease, hypertension, mental retardation, obesity, Alzheimer's, schizophrenia