Chapter 15

Question 1

Chromosome theory of inheritance

Answer 1

Mendelian genes have specific locations along chromosomes, and it is the chromosomes that undergo segregation and independent assortment
A specific gene is carried on a specific chromosome

Question 2

Females have… Males have…

Answer 2

Homologous X chromosomes

One X and one Y

Question 3

Wild type

Answer 3

The phenotype for a character most commonly observed in natural populations

Question 4

Mutant phenotypes

Answer 4

Traits that are alternatives to the wild type

They are due to alleles assumes to have originated as changes/mutations

Question 5

Each egg receives

Answer 5

One chromosome

Question 6

The Y chromosome is much smaller than

Answer 6

The X chromosome

Question 7

Sperm receives

Answer 7

Half of sperm receives X chromosomes and the other half receives Y chromosomes

Question 8

Sex-linked gene

Answer 8

A gene located on either sex chromosome

Question 9

Y-linked genes

Answer 9

Genes located on the Y chromosome

Question 10

X-linked genes

Answer 10

Genes located on the X chromosome

Question 11

Hemizygous

Answer 11

Describes X-linked genes

Instead of hetero and homo

Question 12

Any male receiving the recessive allele from his mother will

Answer 12

Express the trait

Question 13

The cells of females and males have

Answer 13

The same effective dose (one copy) of most X-linked genes

Question 14

Barr body

Answer 14

The inactive X in each cell of a female condenses into a compact object
Lies along the inside of the nuclear envelope

Question 15

Most of the genes of the X chromosome that forms the Barr body are

Answer 15

Not expressed

Question 16

Females have a mosaic of two types of cells

Answer 16

Those with the active derived from the father and those with the active derived from the mother

Question 17

After an X chromosome is inactivated

Answer 17

All mitotic descendants of that cell have the same inactive X

Question 18

The number of genes in a cell is

Answer 18

Greater than the number of chromosomes
Each chromosome (except Y) has hundreds or thousands of genes

Question 19

Linked genes

Answer 19

Genes located near each other on the same chromosomes end to be inherited together in genetic crosses
Genetically linked

Question 20

Genetic recombination

Answer 20

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

Question 21

Parental types

Answer 21

Inherit a phenotype that matches either of the phenotypes of the P (parental) generation
Matching offspring

Question 22

Recombinant types (recombinants)

Answer 22

Nonparental phenotypes

New combinations

Question 23

Crossing over

Answer 23

Breaks the physical connection between specific alleles of genes on the same chromosome
Accounts for the recombination of linked genes
Occurs while replicated homologous chromosomes are paired during prophase of meiosis I
A set of proteins orchestrates an exchange of corresponding segments of one maternal and one paternal chromatid

Question 24

Each pair of homologous chromosomes lines up independently of other pairs during metaphase I, and crossing over prior to that, during prophase I, can

Answer 24

Mix and match parts of maternal and paternal homologs

Question 25

Genetic map

Answer 25

An ordered list of the genetic loci along a particular chromosome

Question 26

The farther apart two genes are,

Answer 26

The higher the probability that a crossover will occur between them and therefore the higher the recombination frequency

Question 27

The greater the distance between two genes,

Answer 27

The more points there are between them where crossing over can occur

Question 28

Linkage map

Answer 28

A genetic map based on recombination frequencies

Question 29

Map units

Answer 29

Distance between genes

Question 30

Despite being on the same chromosome and being physically connected,

Answer 30

The gees are genetically unlinked; alleles of such genes assort independently, as if they were on different chromosomes

Question 31

Nondisjunction

Answer 31

Occasional mishap
Members of a pair of homologous chromosomes do not move apart properly during meiosis I or sister chromatids fail to separate during meiosis II
One gamete receives two of the same type of chromosome and another gamete receives no copy
Other chromosomes are distributed normally

Question 32

Aneuploidy

Answer 32

A condition… If either of the aberrant gametes unites with a normal one at fertilization, the zygote will also have an abnormal number of particular chromosomes

Question 33

Monosomic

Answer 33

Fertilization involving a gamete that has no copy of a particular chromosome will lead to a missing chromosome in the zygote… called for that chromosome

Question 34

Trisomic

Answer 34

If a chromosome is present in triplicate in the zygote… called for that chromosome

Question 35

Polyploidy

Answer 35

More than two complete chromosome sets in all somatic cells

Question 36

Deletion

Answer 36

Occurs when a chromosomal fragment is lost

Affected chromosome is missing certain genes

Question 37

Duplication

Answer 37

Deleted fragment may become attached as an extra segment to a sister chromatid, producing…

Question 38

Inversion

Answer 38

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

Question 39

Translocation

Answer 39

Fragment joins a nonhomologous chromsome, rearrangement called…

Question 40

Genomic imprinting

Answer 40

Variation in phenotype depending on whether an allele is inherited from the male or female parent

Question 41

Genomic imprinting occurs

Answer 41

During gamete formation and results in the silencing of a particular allele of certain genes

Question 42

Not all of a eukaryotic cell’s genes are located on nuclear chromosomes, or even in the nucleus, some genes are located

Answer 42

In organelles in the cytoplasm

These genes are called extranuclear genes or cytoplasmic genes