Chapter 15 : The Chromosomal Basis Of Inheritance

Question 1

Chromosome Theory of Inheritance

Answer 1

Genes occupy specific positions on chromosomes, and it’s the random alignment of pairs of homologous chromosomes at the metaphase 1 and the separation of homologs in anaphase 1 that result in independent assortment and segregation of alleles in gamete formation.

Question 2

The normal phenotype found most commonly in nature; represented by what

Answer 2

Wild type; a superscript

Question 3

Alternative traits, assumed to have arisen as mutations

Answer 3

Mutant phenotypes

Question 4

Females are XX, and produce eggs that each have an X chromosome. What are males?

Answer 4

Males are XY, and produce two kinds of sperm, each with either an X or a Y chromosome

Question 5

Whether the gonads of an embryo develop into tested or ovaries depends on the presence or absence of what gene

Answer 5

SRY gene

Question 6

Where is the SRY gene found

Answer 6

On the Y chromosome

Question 7

Genes located on either sex chromosome are called :

Answer 7

Sex-linked genes

Question 8

Approximately how many genes are located on the Y chromosome, and where are about half of these genes expressed?

Answer 8

78; in the testis

Question 9

Approximately how many genes are located on the X chromosome?

Answer 9

1,100

Question 10

From where do males inherit X-linked alleles

Answer 10

The mother

Question 11

Where do daughters inherit X-linked alleles

Answer 11

Both parents

Question 12

What condition is a result of a lack of a key muscle protein

Answer 12

Duchenne muscular dystrophy

Question 13

What trait is characterized by excessive bleeding due to the absence of one or more blood-clotting proteins

Answer 13

Hemophilia

Question 14

After X inactivation, the other X chromosome is contracted into the Barr body. Where is this located?

Answer 14

Inside the nuclear membrane

Question 15

Both males and females having an equal dosage of most X-linked genes is a result of what

Answer 15

X inactivation

Question 16

Is the selection of which X chromosome to be inactivated planned or a random event

Answer 16

Random event in embryonic cells

Question 17

Genes located near eachother on the same chromosome tend to be inherited together. What are these called

Answer 17

Linked genes

Question 18

Offspring with combos of traits that are different from those of either P generation parent is a result of what

Answer 18

Genetic Recombination

Question 19

What is a genetic map

Answer 19

An ordered list of genes on a chromosome

Question 20

Recombination frequency

Answer 20

Percentage of recombinant offspring produced in a genetic cross

Question 21

What did A.H. Sturtevant suggest about recombination frequencies

Answer 21

That they reflect the relative distance between genes

Question 22

Is the probability of crossing over occurring greater or lesser if the genes are farther apart

Answer 22

Greater

Question 23

When does nondisjunction occur?

Answer 23

When a pair of homologous chromosomes does not separate properly in meiosis 1, or when sister chromatids do not separate in meiosis 2.

Question 24

Sometimes a gamete receives either two copies or no copies of a chromosome. What is this a result of?

Answer 24

Non disjunction

Question 25

A nontypical number of a particular chromosome

Answer 25

Aneuploidy

Question 26

What is the chromosome number if a zygote is trisomic for that chromosome?

Answer 26

2n+1

Question 27

What is the chromosome number if a zygote is monosomic for that chromosome?

Answer 27

2n-1

Question 28

A chromosomal alteration in which an organism has more than two complete chromosomal sets (like triploidy or tetraploidy)

Answer 28

Polyploidy

Question 29

Chromosome fragments that are lost

Answer 29

Deletion

Question 30

When chromosome fragments join to a sister chromatid

Answer 30

Duplication

Question 31

When chromosome fragments break off, join a sister chromatid, and rejoin the original chromosome in the reverse orientation

Answer 31

Inversion

Question 32

When chromosome fragments break off, join a sister chromatid, then join a nonhomologous chromosome

Answer 32

Translocation

Question 33

What is the difference between an organism with a trisomy and a triploid organism?

Answer 33

Trisomy means there is an extra chromosome (2n+1), but a triploid organism has a whole nother complete set of chromosomes.

Question 34

What is Down syndrome also known as?

Answer 34

Trisomy 21