AP Biology - Genetics Vocab

True Breeding

parents have only 1 trait type (homozygous)

P Generation

Parental generation - where you start the experiment

F Generation

Filial generation - child/offspring generation

Cross pollination

Breeding two different individuals

Self-Pollination

Self-fertilize

Allele

Variation of a gene - different __ vary in the sequence of nucleotides (DNA) at the specific locus of a gene

Dominant vs Recessive generic

D: generally the functional protein that masks other alleles. R: Allele makes a malfunctioning protein

Phenotype vs Genotype

P: description of an organism’s physical trait. G: description of an organism’s genetic makeup

Test cross

taking an unknown dominant and crossing it with a recessive. based on offspring, can determine dominant parent

Punnett Squares - ratios

predict outcomes of a genetic cross - expected (e)

Law of segregation

during meiosis, alleles ___ (separate evenly). each allele for a trait is packaged into separate gamete

Law of independent assortment

states that homologous pairs do not influence each other when they line up in Metaphase I (inc. diversity)

Rule of Multiplication and Addition

M: different events get multiplied. A: Same event results get summed together

Incomplete Dominance

heterozygote shows an intermediate, blended phenotype

Codominance

2 alleles affect the phenotype equally and separately (ex. spots)

Genetics of Blood types in Humans

ABO blood groups - example of codominance and multiple allele (3)

Pleiotropy

most genes - one gene affects more than one phenotypic character. (ex. gene affects heart, brain, skin)

Epistasis

(light switch) one gene completely masks out another gene

Polygenic Inheritance

some phenotypes are determined by additive effects of 2 or more genes on a single character

S.ex linked traits

genes are on s.ex chromosomes as opposed to autosomal

Hemophilia

blood-clotting disease (lack ability) - s.ex-linked

X inactivation

females inherit 2 X chromosomes - one X becomes inactivated during embryonic development, condensing into barr body (patchwork trait = mosaic)

Sex influenced traits

autosomal trait is influenced by sex hormones (has age effect) dominant in males, recessive in females (ex. balding)

Environmental effects

phenotype is controlled by both environment (nurture) and genes (nature) - epigenetics

Gene Map - Linked Genes

genes on the same chromosomes - the further apart they are from each other, the higher the crossover rate

Gene mutations

deletion, duplication, inversion, translocation

Pedigree analysis

2 unaffected give to affected (autosomal recessive) 2 affected give to unaffected (autosomal dominant) almost all affected are males (s.exlinked recessive)

Recessive diseases

allele codes for either a malfunctioning protein or no protein

Heterozygotes

have normal phenotype b/c one normal allele produces enough of required protein

Cystic Fibrosis

autosomal recessive - lung issue. normal allele codes for membrane protein

Tay-Sachs

autosomal recessive - CNS/brain issue. non-functional enzyme fails to break down lipids in brain cells

Sickle Cell Anemia

autosomal recessive - blood. mutation of a single amino acid in hemoglobin

Heterozygote advantage

a phenomenon where individuals w/ two different alleles for a gene (heterozygotes) have higher fitness (survival or reproductive success) than those w/ two identical alleles (homozygotes)

Huntington’s disease

autosomal dominant - kills nervous system, starts at age 30-50

Genetics and culture

fairly unlikely that 2 unrelated carriers of same rare harmful recessive allele will meet and mate (matings of close relatives increase risk)

P.K.U.

autosomal recessive - results in a nonexistent enzyme (processing 1 of 20 amino acids) build up can cause irreversible brain damage

Nondisjunction

chromosomes don’t separate properly during meiosis

Breakage of chromosomes

deletion, duplication, inversion, translocation

Nondisjunction meiosis I

I: homologous chromosomes fail to separate - affects all 4 resulting gametes (two with n+1, two with n-1)

Nondisjunction meiosis II

II: - sister chromatids fail to separate - affects only half the gametes (two normal, one n+1, one n-1) less severe than I

Trisomy

aneuploidy: cells have 3 copies of a chromosome

Monosomy

aneuploidy: cells have only 1 copy of a chromosome

Downs syndrome

s.ex chromosome aneuploidy (less severe effects b/c redundancy) trisomy 21

Genetic testing

Amniocentesis in 2nd trimester - sample of embryo cells

S.ex chromosome nondisjunction

produces a variety of distinct syndromes in humans (development more tolerant of wrong numbers in s.ex chromosome)

Kleinfelters

XXY sterile male

Jacobs

XYY male

Trisomy X

XXX female

Turners

XO female - only survivable monosomy