The Chromosomal Basis of Inheritance

Question 1

What is the chromosome theory of inheritance?

Answer 1

The theory that chromosomes are linear sequences of genes. The unifying theory stating that inheritance patterns may be generally explained by assuming that genes are located in specific sites on chromosomes

Question 2

Why did Morgan chose the fruit fly as his experimental organism?

Answer 2

Easy to work with; reproduce quickly; autosome and sex chromosome

Question 3

What did Morgan discover amongst the fruit flies he was examining?

Answer 3

Mutation in eye color- white eyed males

Question 4

What is wild type?

Answer 4

What is commonly seen in the population

Question 5

What is mutant phenotype?

Answer 5

Mutant phenotype is uncommon in the population

Question 6

What is hemizygous and what does it mean genetically?

Answer 6

One allele on the X chromosome no corresponding on the Y (usually)

Question 7

What is homogametic?

Answer 7

Makes one type of gamete

Question 8

What is heterogametic?

Answer 8

makes two types of gametes

Question 9

What is the chromosomal basis of sex in humans?

Answer 9

The X-Y system

Question 10

What is the chromosomal basis of sex in grasshoppers, cockroaches, and some other insects?

Answer 10

The X-0 system (males don’t have sex chromosome)

Question 11

What is the chromosomal basis of sex in birds, some fishes and insects?

Answer 11

The Z-W system (female hemizygous with ZW and male homo ZZ)

Question 12

What is the chromosomal basis of sex in most bees and ants?

Answer 12

The halo-diploid system (female 32 male 16)

Question 13

What does SRY stand for? What does the SRY gene code for?

Answer 13

Gene on the Y chromosome; stands for Sex determining Region of Y; it codes for the development of testis (codes for the protein that does the development)

Question 14

What do we mean by “sex linked genes”?

Answer 14

Found on the sex chromosomes

Question 15

What is so different about the inheritance of Y-linked and X-linked genes?

Answer 15

Everyone gets an x; only half get a y

Question 16

What is a Barr body and what does its presence mean?

Answer 16

A chromosome is heterochromatic meaning very condensed–> that one will not show phenotypically

Question 17

When does X inactivation in female mammals occur and what does that mean?

Answer 17

50/50 an which one is inactive and means that the one that is active will be dominant

Question 18

What is nondisjunction and how does it result in abnormal chromosome numbers?

Answer 18

When the chromosomes in meiosis I or the chromatids in meiosis II are not separating

Question 19

What is aneuplodiy?

Answer 19

Too many or too few chromosomes

Question 20

What is a deletion in chromosome structure?

Answer 20

A deletion removes a chromosomal segment; CHANGES ALLELE NUMBER

Question 21

What is duplication in chromosome structure?

Answer 21

Duplication repeats a segment; CHANGES ALLELE NUMBER

Question 22

What is inversion?

Answer 22

Reverses a segment within a chromosome; NOCHANGE in number

Question 23

What is translocation?

Answer 23

Moves a segment from one chromosome to a non homologous chromosome; NO CHANGE in number

Question 24

What is it called when you have 3 21 chromosomes?

Answer 24

trisomy; down syndrome

Question 25

What is is called when a male has an extra X

Answer 25

Clinefeller’s syndrome

Question 26

What is it called when a male has an extra Y

Answer 26

Jacobs syndrome

Question 27

What is is called when a female has an extra X

Answer 27

Trisomy X

Question 28

What is it called when a female is missing an X

Answer 28

Monosomy X; Turners Syndrome

Question 29

What is is called when you have a deletion in chromosome 5

Answer 29

Cri-du-chat syndrome