chapter 15: chromosomal basis of inheritance

Question 1

what is sex-linked gene?

Answer 1

a gene located on either sex chromosome

Question 2

what is a X linked gene?

Answer 2

a gene located on the X chromosome, showing a distinctive pattern of inheritance

Question 3

what determines the sex of humans, grasshoppers, chickens, and bees?

Answer 3

humans: XX female and XY male
grasshoppers: XX female and XO male
chickens: ZW female and ZZ male
bees: diploid female and haploid male

Question 4

what two disabilities are considered X linked traits?

Answer 4

color blindness and hemophilia

Question 5

what is the disease hemophilia?

Answer 5

is an X-linked recessive disorder defined by the absence of one or more of the proteins required for blood clotting (when a person is injured, bleeding is prolonged because a firm clot is slow to form)

Question 6

what is genetic recombination?

Answer 6

a new combination of the alleles inherited from parents

Question 7

alleles of unlinked genes are recombined by what process?

Answer 7

independent assortment

Question 8

alleles of linked genes are recombined by what process?

Answer 8

crossing over

Question 9

how is the law of independent assortment and the law of segregation different?

Answer 9

law of segregation: states how alleles of a gene are segregated into two gametes and reunite after fertilization
law of independent assortment: states how alleles of different genes independently segregate from each other during the formation of gametes

Question 10

what is a genetic map?

Answer 10

an ordered list of genetic loci (genes/ other genetic markers) along a chromosome

Question 11

what are centimorgans?

Answer 11

a unit of measure for the frequency of genetic recombination

Question 12

what are map units? how are map units estimated?

Answer 12

a unit of measurement of the distance between genes, one map unit is = to a 1% recombination frequency

Question 13

when is recombination of linked genes more likely? when the genes are 10 centimorgans apart or 25 centimorgans apart?

Answer 13

25 centimorgans apart

Question 14

what is the relationship between genes and chromosomes?

Answer 14

genes are located on chromosomes

Question 15

what is the sex chromosomes of females and males?

Answer 15

female: 2 X chromosomes
male: 1 X and 1 Y chromosome

Question 16

what is the chromosome theory of inheritance?

Answer 16

principle stating: genes have a specific loci (position) on chromosomes & chromosomes undergo segregation (separation) and independent assortment

Question 17

what are autosomes?

Answer 17

any chromosome, except sex chromosomes

Question 18

are genes more likely to be found on the X chromosome of the Y chromosome?

Answer 18

on the X chromosome

Question 19

what are linked genes?

Answer 19

located on the same chromosome (they tend to be inherited together)

Question 20

what are unlinked genes?

Answer 20

located on 2 separate homologous chromosomes

Question 21

what must an organism be to be considered “true-breeding”?

Answer 21

homozygous

Question 22

when is crossing over most likely to occur?

Answer 22

the further apart genes are

Question 23

are sex chromosomes homologous?

Answer 23

no

Question 24

which chromosome is bigger X or Y?

Answer 24

X is much bigger