Chapter 15 (Chromosomal Theory)

Question 1

What are Mendel’s “factors”?

Answer 1

segments of DNA located along

chromosomes

Question 2

What is the chromosomal theory of inheritance?

Answer 2

Mendelian genes have specific loci (positions) along

chromosomes, and it is the chromosomes that undergo segregation and independent assortment

Question 3

Who is Thomas Hunt Morgan?

Answer 3

provided evidence that a specific gene with a specific chromosome existed

Question 4

What did Thomas Hunt experiment on?

Answer 4

fruit flies (Drosophila melanogaster)

Question 5

Why were fruit flies a good choice for Thomas Hunt to experiment on?

Answer 5

production of hundreds of offspring, new-generation forms every two weeks, easily distinguishable chromosomes

Question 6

What is the wild type?

Answer 6

dominant (most abundant)

Question 7

What is mutant type?

Answer 7

recessive (alt. form of wild type)

Question 8

What change was significant in Hunt’s experiment and what did it explain?

Answer 8

only male had white eyes instead of the usual red, suggesting that mutation was sex-linked and it supported the theory of chromosomal inheritance

Question 9

What is the notation for white eyes?

Answer 9

w

Question 10

What is the notation for red eyes?

Answer 10

w+

Question 11

What is a sex-linked gene?

Answer 11

gene located on sex chromosome

Question 12

What are X-linked genes?

Answer 12

gene on X chromosome

Question 13

What are Y-linked genes?

Answer 13

genes located on Y chromosome

Question 14

What is a parental type?

Answer 14

looks like parent

Question 15

What is a recombinant type?

Answer 15

looks like a mix of parents

Question 16

What is the distance between genes if they are to be inherited together?

Answer 16

they have to be close together (unit wise)

Question 17

What are serious x-linked diseases?

Answer 17

Duchenne muscular dystrophy and hemophilia (blood clotting gone)

Question 18

What do dominant x genes affect?

Answer 18

physical

Question 19

What do recessive genes affect?

Answer 19

enzymatic level

Question 20

How can linked genes be inherited together?

Answer 20

they are located near each other on the same chromosome, they don’t sort independently and can affect the inheritance of two traits

Question 21

Do linked genes deviate from Mendel?

Answer 21

yes

Question 22

What is genetic recombination?

Answer 22

production of offspring with combinations of traits that differ from those found in either P generation parent

Question 23

What does a 50% frequency of recombination suggest?

Answer 23

genes located on a different chromosomes or can be very far apart

Question 24

What does a frequency of recombination lower than 50% suggest?

Answer 24

genes are located closely on chromosome

Question 25

What is genetic recombination based on?

Answer 25

Based on crossing over of homologous chromosomes during prophase I of meiosis – exchange of DNA

Question 26

What did Alfred Sturtevant do?

Answer 26

construct the first genetic map that has ordered list of loci along a particular chromosome

Question 27

What is a linkage map?

Answer 27

A genetic map based on recombination frequencies

Question 28

What are map units for a linkage map?

Answer 28

distance between genes for every 1% of genetic recombination frequency

Question 29

When is the physical connection of genes contributing to the idea of unlinked genes?

Answer 29

Despite being on the same chromosome and thus being physically connected, the genes are genetically unlinked; alleles of such genes assort independently, as if they were on different chromosomes

Question 30

What does a linkage map not portray?

Answer 30

physical location of a gene, only shows recombination frequencies

Question 31

What can a large scale chromosomal alteration lead to?

Answer 31

miscarriage or developmental issues

Question 32

What structure is supposed to distribute chromosomes to daughter cells without error?

Answer 32

mitotic spindle

Question 33

What is nondisjunction?

Answer 33

members of a pair of homologous chromosomes do not move apart properly during meiosis I or sister chromatids fail to separate during meiosis I (aka one gamete receives both pairs whereas the other game doesn't receive anything)

Question 34

What is aneuploidy?

Answer 34

zygote has an abnormal number of a chromosome (think a for abnormal)

Question 35

What is monosomic?

Answer 35

the aneuploid zygote that is missing a chromosome (2n-1) (mono for one less)

Question 36

What is trisomic?

Answer 36

aneuploid zygote that has one extra chromosome (2n+1) (tri for 3, 1 extra)

Question 37

When does monosomic and trisomic occur?

Answer 37

in fertilization

Question 38

What is polyploidy?

Answer 38

an organism has more than two complete sets of chromosomes

Question 39

Which one has a more detrimental affect, aneuploidy or polyploidy?

Answer 39

aneuploidy

Question 40

What are the different types of changes in chromosomes from errors in meiosis crossing over?

Answer 40

deletion, duplication, inversion, translocation

Question 41

What is deletion?

Answer 41

the chromosomal fragment is lost

Question 42

What is duplication?

Answer 42

“deleted” fragment may become attached as an extra segment to a sister or non-sister chromatid

Question 43

What is an inversion?

Answer 43

A chromosomal fragment may also reattach to the original chromosome but in the reverse orientation

Question 44

What is translocation?

Answer 44

fragment to join a nonhomologous chromosome

Question 45

How are deletion and duplication related?

Answer 45

nonsister chromatids sometimes exchange unequal-sized segments of DNA, so that one partner gives up more genes than it receives products of such an unequal crossover are one chromosome with a deletion and one chromosome with a duplication

Question 46

What is an aneuploid condition?

Answer 46

Down syndrome

Question 47

What causes Down syndrome?

Answer 47

three copies of chromosome 21 (become trisomic)

Question 48

What does Down Syndrome affect?

Answer 48

facial features, short stature, correctable heart defects, and developmental delays

Question 49

In the mother, how does down syndrome frequency increase?

Answer 49

with age

Question 50

What does nondisjunction in meiosis result in?

Answer 50

aneuploidy

Question 51

What happens in the aneuploidy of sex chromosomes?

Answer 51

Y chromosome carries relatively few genes or extra copies of the X chromosome

Question 52

What is Klinefelter syndrome?

Answer 52

an extra inactive X chromosome in a male (XXY) and it affect reproductive organs, Males can also display an extra Y chromosome (XYY)

Question 53

Are females with XXX healthy or no?

Answer 53

healthy because the X is inactive

Question 54

What is Turner syndrome?

Answer 54

only one X chromosome, are sterile because | their sex organs do not mature

Question 55

How does a female and male have the same level of protein production?

Answer 55

female's extra X is inactivated so one X in both male and female work

Question 56

What is a Barr body?

Answer 56

inactive X chromosome in each cell of a female condenses into a compact object

Question 57

When are Barr bodies reactivated?

Answer 57

to make eggs

Question 58

Is the determination of which X chromosome get's inactivated in females random or not?

Answer 58

it is random and independent (1 of the X in XX will get deactivated, but which one?)

Question 59

What are mosaic cells and where are they found?

Answer 59

found in females, e with the active X derived from the father and those with the active X derived from the mother, when a person has 2 or more genetically different sets of cells in his or her body.

Question 60

If a female is heterozygous, what happens to her mosaic cells?

Answer 60

half of her cells will express one allele, while the others will express the alternate allele (ex: recessive mutation can lead to some patches of skin will have sweat glands while others will not)