Morgan and some mendel

Question 0

Morgan experiments with ..

Answer 0

fruit flies, provided convincing evidence that chromosomes are the location of mendel’s heritable factors

Question 1

The first solid evidence associating a specific gene with a specific chromosome came from:

Answer 1

Thomas Hunt Morgan, an embryologist

Question 2

Characteristics the make fruit flies a convenient organism for genetic studies :

Answer 2

• They breed at a high rate
• a generation can e bred every two weeks
• they have only four pairs of chromosomes

Question 3

Morgan noted wild type, or normal, phenotypes that were common in the fly population..

Answer 3

traits alternative to the wild type are called mutant phenotypes

Question 4

in one experiment, he mated male flies with white eyes (mutant) with female flies with red eyes (wild type) the results were:

Answer 4

the F1 generation all had red eyes

the F2 generation showed the 3:1 read :white eye ratio but only males had white eyes

Question 5

sex plinked genes exhibit unique patterns of inheritance

Answer 5

• in humans and some other animals, there is a chromosomal basis of sex determination
• in humans and other mammals, there are two varieties of sex chromosomes: a larger X chromosomes and a smaller Y chromosome

Question 6

only the ends of the Y chromosome have regions that are …

Answer 6

homologous with the X chromosome

Question 7

The SRY gene on the Y chromosome codes for the development of

Answer 7

testes

Question 8

Females are

Answer 8

XX

Question 9

Males are

Answer 9

XY

Question 10

Each ovum contains and X chromosome, while a sperm may contain

Answer 10

either and X or a Y

Question 11

Other animals than humans have different methods of …

Answer 11

sex determination

Question 12

inheritance of sex-linked genes

Answer 12

the sex chromosomes have genes for many characters unrelated to sex

Question 13

a gene located on either sex chromosome is called a

Answer 13

sex-linked gene
they follow specific patterns of inheritance
(in humans it usually refers to a gene on the larger x chromosome)

Question 14

for a recessive sex-linked trait to be expressed

Answer 14

a female need two copies of the allele

a male needs only one copy of the allele

Question 15

Linked genes tend to be inherited together because…

Answer 15

they are located near each other on the same chromosome

Question 16

each chromosome has..

Answer 16

hundreds or thousand of genes

Question 17

linked genes

Answer 17

genes located on the same chromosome that tend to be inherited together

Question 18

Morgan did other experiments with fruit flies to see how linkage affects inheritance of two characters: he crossed flies that differed in traits of body colour and wing size. the results were:

Answer 18

colour and wing size are usually inherited together in specific combinations (parental phenotypes) he notes that these genes do not assort independently, and reasoned that they were on the same chromosome (but non parental phenotypes were also produced)

Question 19

genetic recombination

Answer 19

the production of offspring with combinations of traits differing from either parent

Question 20

the genetic finding of mendel and morgan relate to the …

Answer 20

chromosomal basis of recombination

Question 21

Mendel observed that combinations of traits in some offspring differ from either parent.
Parental types:

Answer 21

offspring with a phenotype matching one of the parental phenotypes

Question 22

offspring with nonparental phenotypes (new combination of traits):

Answer 22

recombinant types or recombinants

Question 23

a 50% frequency of recombination is observed for :

Answer 23

any two genes on different chromosomes

Question 24

genes can be linked, but the linkage was incomplete,

Answer 24

as evident from recombinant phenotypes

Question 25

some process must sometimes break the physical connection between genes on the same chromosome

Answer 25

crossing over of homologous chromosomes

Question 26

genetic map

Answer 26

an ordered list of the genetic loci along a particular chromosome
(the farther apart two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency)

Question 27

linkage map

Answer 27

genetic map of a chromosome based on recombination frequencies

Question 28

distances between genes can be expressed as :

Answer 28

map units; one map unit or centimorgan represent a 1% recombination frequency

Question 29

genes that are far apart on the same chromosome can have a recombination frequency near ..

Answer 29

50%

such genes are physically linked, but genetically unlinked, and behave as if found on different chromosomes

Question 30

Abnormal chromosome number:

nondisjunction

Answer 30

pairs of homologous chromosomes do not separate normally during meiosis
as a result, one gamete receives two of the same type of chromosome, and another gamete receives no copy

Question 31

Aneuplodiy

Answer 31

results from the fertilization of gametes in which nondisjunction occurred (offspring with this condition have an abnormal number of a particular chromosome)

Question 32

polyploidy

Answer 32

is a condition in which an organism has more than two complete sets of chromosomes
triploidy (3n) is three sets of chromosomes
common in plants but not animals

Question 33

breakage of a chromosome can lead to four types of changes in chromosome structure:

Answer 33

deletion
duplication
inversion
translocation

Question 34

deletion

Answer 34

removes a chromosomal segment

Question 35

duplication

Answer 35

repeats a segment

Question 36

inversion

Answer 36

reverses a segment within a chromosome

Question 37

translocation

Answer 37

moves a segment from one chromosome to another