SEX-LINKED TRAITS AND SEX-LINKED PATTERNS OF INHERITANCE

Question 1

____of an individual is determined by the ____contributed to the zygote by the sperm and the egg

Answer 1

sex

sex chromosomes

Question 2

• An egg can donate an

• A sperm can donate an

Answer 2

X

X or Y

Question 3

Therefore the___ determines the sex of a child

Answer 3

sperm

Question 4

In humans, sex is determined by the _____pair

Answer 4

23 rd chromosome

Question 5

• Humans egg cells always have an ____ chromosome

• Human sperm cells have____chromosomes

Answer 5

X

either an X or a Y chromosome

Question 6

• If a sperm with an X fertilizes the egg, the 23 rd pair will be____ and it will be a female

• If a sperm with a Y fertilizes the egg, the 23 rd pair will be ___and it will be a male

Answer 6

XX

XY

Question 7

SEX-LINKED INHERITANCE

• Using____ as test subjects,____ studied eye colour using simple monohybrid crosses.

• Red eyes (R) are dominant over white eyes (r).

Answer 7

fruit flies

Thomas Morgan

Question 8

SEX-LINKED INHERITANCE

• When he crossed purebred white-eyed males with red-eyed females, he was unable to produce a female with white eyes.

• He concluded that the gene must be located on the

Answer 8

X chromosome

Question 9

SEX CHROMOSOMES CAN CARRY OTHER GENES TOO = _________________

Answer 9

SEX LINKED TRAITS

Question 10

Traits carried on the sex chromosome (23rd pair in humans); most are carried on the X chromosome

Answer 10

Sex-linked traits

Question 11

• Most known sex-linked traits are____

• This is probably because the___ chromosome is much larger than the___ chromosome.

Answer 11

X-linked (carried on the X chromosome)

X
Y

Question 12

The inheritance of traits that are located on the _____depends on the sex of the parent carrying the trait.

Answer 12

sex chromosomes

Question 13

•_____ show up in different % in males and females because they move with the sex chromosomes

•____ linked genes show up in males.

Answer 13

SEX LINKED TRAITS

Y

Question 14

Sex-linked traits are inherited differently in men and women –

____have two X chromosomes, so they have 2 genes for all traits carried on the 23 rd pair

____have one X chromosome, so they only have 1 gene for all traits carried on the 23 rd pair

Answer 14

Females

Males

Question 15

Whether or not recessive sex-linked traits get passed on depends on the sex of the parent and the sex of the offspring

• Males pass their X chromosome (and its genes) to all of…..

• Females pass one of their X chromosomes (and its genes) to all of…

Answer 15

their daughters and none of their sons

their children

Question 16

Sex-linked Inheritance

Answer 16

1. Sex-linked Dominant Inheritance
2. Sex-linked Recessive Inheritance

Question 17

• Refers to situations where a single dominant allele on the X chromosome can lead to a trait/condition

Answer 17

X – Linked Dominant Inheritance

Question 18

Sex-linked Dominant Inheritance

1. The trait does not skip generations.
2. Affected males must come from affected_____.
3. Approximately____ the children, both sons and daughters, of an affected heterozygous female are affected.
4. Affected females come from affected…
5. All the….., of an affected father are affected.

Answer 18

mothers

half

mothers or fathers.

daughters, but none of the sons

Question 19

• Refers to those situations where a recessive allele on the X chromosome can lead to a trait/condition or disorder.

Answer 19

X – linked Recessive Inheritance

Question 20

Sex-linked Recessive Inheritance

1. Most affected individuals are__.
2. All daughters of an affected male will be_____ and all sons will be____.
3. Affected males result from _____ who are affected or who are known to be carriers because they have affected brothers, fathers or maternal uncles
4. Affected females come from affected….
5. All the sons of affected____ should be affected.
6. Approximately half the sons of carrier____ should be affected.

Answer 20

male

carriers\ unaffected

Mothers

fathers and affected or carrier mothers

females

females

Question 21

X – linked Recessive Inheritance

• Males are affected more often than females. Ratio of…

• Affected____ will transmit the allele to all daughters, but not to sons.

• Homozygous recessive____ can arise only from matings in which the father is affected and the mother is affected or a carrier

Answer 21

8:1

males

females

Question 22

Genes carried on Y chromosome

Answer 22

Y-LINKED GENES