extending mendelian genetics study guide

30 terms by nedger 

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polygenic traits

many genes determine the phenotype; hair color, skin color, etc.

environment

In addition to genotype, ___________ also affects phenotype.

pedigree

a chart that traces the phenotypes and genotypes within a family

sex-linked trait

the gene for this type of trait is found on an sex chromosome; mostly males will exhibit this type of trait

XY

what is the genotype of a male human?

incomplete dominance

neither allele totally masks the expression of the other allele; the offspring's phenotype will be a blend of the parents' phenotypes

codominance

both alleles are expressed simultaneously

female

who could be a carrier for an X-linked trait such as colorblindness?

carrier

a person who is heterozygous for a disorder and who does not have the disorder but can pass the disorder to offspring

x-chromosome inactivation

one of the x chromosomes in each of the cells of female mammals is randomly turned off

autosomes

type of chromosomes that determine most of the traits expressed in a person's phenotype

men have one X and one Y chromosome--therefore there is no second X chromosome to mask the expression of a trait found on the X chromosome, whereas women have two X chromosomes

why are recessive sex-linked traits more common in men than in women?

epistatic gene

a gene that controls the expression of other genes

karyotype

a picture of all of the chromosomes in a cell, with homologous chromosomes paired and lined up according to size; can show the presence of extra or missing chromosomes, but does not provide information about specific genes

Barr body

formed when one of the X chromosomes in a female cell is inactivated

autosomal disorder

type of disorder in which one of the parents must display the trait in order for a child to display the trait

recessive disorder

type of disorder that can skip a generation; both parents must carry an allele for the trait

sex-linked disorder

type of disorder in which the mother must be a carrier

shaded symbols

these symbols represent individuals that display a particular trait

23

how many pairs of chromosomes are found in humans?

single

gametes contain a _________ copy of each chromosome

50%

What is the probability that two parents that are heterozygous for a dominant allele located on an autosome will produce a child that displays the dominant trait?

25%

What is the probability that two parents that are heterozygous for a recessive allele located on an autosome will produce a child that displays the dominant trait?

two recessive alleles

For an XX female to express a recessive sex-linked trait, she must have

alleles

What do the letters in a Punnett square represent?

phenotype; genotype

your physical appearance is known as your _____, whereas the actual genes that you have are your _____

yes; Both parents would need to be heterozygous so that the child could inherit the two alleles needed for type O

Is it possible for a couple with blood types A & B to have a child that is type O? Explain

type A, type AB, or type B, depending on whether the type A parent was homozygous or heterozygous

What blood type could a child have if its parents were type AB and type A?

type A or type O (if the type A parent was heterozygous)

What blood type could a child have if its parents were type A and type O?

ABO blood groups

dominant and recessive alleles, codominance, and multiple alleles are all exhibited by what human phenotype?

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