chapter 12: inheritance patterns and human genetics

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chromosomes and inheritance

sex chromosomes- X and Y chromosomes, and contains genes that determine gender

autosomes- chromosomes that are not directly involved in determining the sex of the individual

female~ xx

male~ xy

the sperm determines the gender of the offspring

sex-linked trait- a trait that is coded for by an allele on the sex chromosome

more sex linked traits on the x chromosome than on the y chromosome

color blindness in males are more likely

linked genes- a pair of genes that tend to be inherited together

linkage group- set of linked genes

on the same chromosome

x-linked traits- traits that are controlled by genes found on the x chromosome

sex- influenced traits- autosomal traits that are influenced by sex

pattern baldness

chromosome map- diagram that shows the linear order of genes on a chromosome

where the gene is located on a chromosome

map unit- a frequency of crossing-over of 1 percent

germ cell mutations- occur in an organisms gametes. Do not affect the organism but may be passed on to offspring

somatic cell mutations- occur in an organisms body cells and affect the organism and cannot be inherited.

some types of skin cancer or leukemia

lethal mutations- cause death, before birth

beneficial mutations affect the organisms appearance and have a better chance of surviving and reproducing

deletion- loss of a piece of a chromosome due to breakage

inversion- chromosomal segment breaks off, flips backward, and reattaches to a nonhomologous chromosome

nondisjunction- chromosome fails to separate from its homologue during meiosis

disorders due to nondisjunction

monosomy

trisomy

down syndrome

translocation- piece of a chromosome breaks off and attaches to a nonhomologous chromosome

point mutation- the substitution, addition, or removal of a single nucleotide

change that occurs within a single gene or other segment of DNA on a chromosome

substitution- one nucleotide replaces another

occurs in a codon

amino acid can be changed

deletion mutation- one or more nucleotides in a gene are lost

frame shift mutation- incorrect grouping of the remaining codons

makes all the amino acids downstream change

can have a disastrous effect on the protein's function

insertion mutations- one or more nucleotides are added to a gene

may also result in a frame shift mutation

chromosome map

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Human genetics

pedigree- a diagram that show how a trait is inherited over several generations

square-male

circle-female

filled- person has trait

horizontal line show mating

patterns of inheritance- expression of genes over generations

autosomal- appear in both sexes equally

sex linked- appear only in males

autosomal dominant-every one with the trait has parent with the trait (huntington's)

recessive- person with the trait can have 1, 2, or neither parent show the trait (sickle cell)

homo/hetero dom-phenotype shows dom characteristic (same for rec)

carriers- don't have the disease but have 1 copy of the recessive allele

genetic disorder- diseases or disabling conditions that have a genetic basis

polygenic- influenced by several genes

show many degrees of variation

most human characteristics

skin color/eye color

complex characters- characters that are strongly influenced by both enviroment and genes

skin color and height

many human condition

multiple alleles- genes with three or more alleles

blood types

codominance- both alleles are shown in the phenotype of a heterzygote

incomplete dominance- individual shows trait that is intermediate between the two parents

straight haired parent+curly haired parent= wavy haired child

sex-influenced traits- involved in other complex characters

usually autosomal

*see sec 1 notes*

single allele traits- controlled by a single allele of a gene

huntington's disease

genetic screening- examination of a person's genetic makeup

amniocentesis- a doctor removes amniotic fluid from the amnion for testing

chorionic villi sampling- doctor takes cells from the zygote from in between the placenta and uterus to test

genetic counseling- the process of informing a person or couple about their genetic makeup

gene therapy- places a healthy copy of a gene into he cells of the person with a defective copy

relies on knowing gene sequences

somatic cell gene therapy- body cells are altered

germ cell gene therapy- egg or sperm cell cells are altered