bio sex linked traits packet quiz

sex chromosomes

the pair of chromosomes that determine the sex of an individual
- the 23rd pair in humans are the sex chromosomes

female

xx

male

xy

autosomes

all other chromosomes other than sex cells
- 1st through 22nd pair in humans

sex-linked

also called x-linked/x-traits; traits that are determined by genes on the x chromosomes
- ex of sex-linked diseases: hemophilia, colorblindness, duchenne muscle dystrophy

hemophilia

not able to plot blood correctly -ex: H= normal h=hemophilia -- female X^H X^H - normal X^H X^h - normal but carrier X^h X^h - hemophiliac -- male (can't be carriers) X^H y - normal X^h y - hemophiliac

colorblindness

inability to distinguish between certain colors

• red/green colorblindness and blue/yellow colorblindness -- H normal h cb.

• bc males only have one x chromosome, any recessive allele on the x chromosome will be expressed -- thus males, are MORE LIKELY to express sex-linked recessive traits

duchenne muscular dystrophy

• gradual weakening and wasting away of muscle tissue -- muscle types: skeletal, smooth and cardiac

• usual onset before age 6, chair-ridden by 12, dead by 20

incomplete dominance

a blending of traits in which neither allele is completely dominant over the other
- ex: snapdragons, hypercholesterolemia (elevated cholesterol)
H - normal H^1 - HC.

multiple allele trait

aka codominance; the existence of more than 2 alleles for a given trait
- ex: blood type in humans

blood type in humans

3 different alleles: I^A, I^B, i -- corresponds to the presence of antigens on the surface of red blood cells

• AB, A, B, and O -- the I^A allele and I^B allele are said to be CODOMINANT to the i allele

AB

phenotype: AB
genotypes: I^A I^B
antigens (surface): A and B
antibodies (in blood): none
special: universal recipient

antigen

protein marker on RBC; on surface

antibodies

in blood

A

phenotype: A
genotypes: I^A I^A or I^A i
antigens: A
antibodies: B
special: none

B

phenotype: B
genotypes: I^B I^B or I^B i
antigens: B
antibodies: A
special: none

O

phenotype: O
genotype: ii
antigens: none
antibodies: both A and B
special: universal donor

+

presence of RH factor

-

absence of RH factor

RH factor

protein/antigen
O+ = 70%
A- = 0.8%

pleiotropy

the impact of a single gene on more than one characteristic
ex: sickle cell anemia

sickle cell anemia

tow abnormal copies of hemoglobin gene result in a variety of different symptoms including: weakness, organ damage, kidney failure, pain, and others

polygenic inheritance

the additive effects of two or more genes on a single characteristic

• skin color, height, eye color in humans

• skin color and eye color based on amount of melanin

environmental affects on gene expression and phenotype

himalayan rabbits and siamese (black ears, tail, paws, and nose; keeping warmth) cats carry an enzyme for melanin production that is heat-sensitive

• enzyme is less active at the surface of warm body parts

• fur color is darker in cooler parts such as ears, limbs, and tail

female

picture

male

picture