Genetics Final

Genetics

The study of hereditary traits

Hereditary

Passed from parents to offspring

Trait

A characteristic such as height, skin color, or eye color

Gene

A unit of heredity that determines a trait

Dominant allele

Allele that is expressed when present

Recessive allele

Allele expressed only when two copies are present

Genotype

The combination of alleles an organism has

Phenotype

The observable physical traits

Homozygous

Having two identical alleles

Heterozygous

Having two different alleles

Gamete

Sex cell carrying one allele per gene

Male-dominated inheritance

all genetic information comes from the father, if the mother follows instructions its a boy, if the mother messes up its a girl

Anton van Leewenhoek

Known as the “microscope man”, propnent of male-dominated inheritance in the 1700s

Gregor Mendel

Father of classical genetics who discovered inheritance patterns

Parental generation (P)

Original organisms in a genetic cross

Sum of (actual - expected )² / expected

X² Statistical test

X² Statistical test

used to see if the observed and expected frequencies difference is significant

degrees of freedom

Number of categories of data - 1

Test cross

Cross with homozygous recessive organism to determine genotype

Pedigree

Diagram showing inheritance in a family

Wild-type

Normal form of a trait

Mutant

Genetic variation from the normal form

Significant

Result with probability less than 0.05

Monohybrid cross

Cross involving one gene

Dihybrid cross

Cross involving two genes

Independent segregation

Alleles of different genes do not influence each other and separate independently

Lethal allele

Allele causing death when homozygous

Semilethal allele

Allele causing partial death when homozygous

Inbreeding

Mating between close relatives increasing homozygosity

• 2 alleles / gene

• 1 allele / gamete

• dominant and recessive alleles

Gregor Mendel’s conclusions

Multiple alleles

Gene with more than two possible alleles

Codominance

Both alleles are expressed equally (sweet & sour)

intermediate inheritance

blend of traits (blue + yellow = green)

Epistasis

One gene controls expression of another

hypostatic

the genes that epistatis genes overrule

Polygenic trait

Trait controlled by many genes

Pleiotropy

One gene affects multiple traits

genotype

genetic make-up

phenotype

physical appearance

Asexual reproduction

Reproduction without sex producing identical offspring

Sexual reproduction

Reproduction producing genetic variation

Chromosome

Coiled DNA containing genes

Chromatin

Uncoiled DNA used for gene expression

Diploid

Cell with two sets of chromosomes

Haploid

Cell with one set of chromosomes

Homologous chromosomes

Pairs with same genes but different alleles

Autosomes

Non-sex chromosomes

XY system

Males XY, females XX

X-linked gene

Gene located on X chromosome

to make it to the next generation

Goal of an allele

Hemizygous

Having only one allele of a gene, (XX)

budding, grafting/fragmentation

types of asexual reproduction

SRY gene

Gene on Y chromosome that triggers male development

Barr body

Inactivated X chromosome

Mosaic

Organism with cells of different genetic expression

meiosis

sexual reproduction. Interphase, then PMAT, then immediately to PMAT again

Murray Barr

discovered barr bodies

Sex-limited traits

traits only in 1 sex (like bull’s horns)

Sex-linked traits

gene on the sex chromosome, assumed to be on the X

• fast

• identical

• no mistakes

Mitosis advantages

• 2 organisms

• 2 sexes

• behavioral difference

• produce gametes

• process to unite gametes

• prone to mistakes

meiosis requirements/ disadvantages (6)

genetic variety

meiosis adv, mitosis disadvantage

Women: XX
Man: X

X0 system

Women: ZW
Man: ZZ

ZW system

Haplodiploidy

reproduction system in which there is no sex chromosomes

parthenogenesis

virgin birth, male aren’t fertilized

Woman: 2N
Man: 1N

haplodiploidy

locus

where traits physically are on a gene

prokaryotic

no nucleas, asexual reproduction

eukaryotic

have nucleas, sexual reproduction

somatic

body cells

Centromere

Region used for chromosome movement

Telomere

End of chromosome that protects DNA and acts as a cellular timer

metacentric

centromere in the middle

submetacentric

centromere makes a short p, longer q

acrocentric

centromere makes a very short p, very long q

telocentric

centromere is at one end

telemerase

enzyme that prevents shortening of telemeres

Mitosis

Cell division producing identical cells

Meiosis

Cell division producing gametes

Gene linkage

Genes located on same chromosome

Cis

Dominant alleles on same chromosome

Trans

Dominant alleles on different chromosomes

karyotype

organized display of all chromosomes

• chromatid pairds form

• nuclear membrane dissolves

• microtubules grow

Prophase (3)

• line up in the middle

• mitotic spindle forms

Metaphase (2)

microtubles contract to the poles

Anaphase

• mitotic spindle breaks

• nuclear membrane forms

• chromatin unravels

• cytokinesis

telephase (4)

• G1 - rest

• S - DNA synthesis (DNA copied)

• G2 - rest

Interphase (3)

• No 2nd interphase in meiosis

• diploid → haploid vs diploid → diploid

Meiosis vs Mitosis (2)

tetrad or synapse

in meisos metaphase 1, the 4 pairs of chromatids line up to form this

polytene chromosomes

chromosomes that are copied but don’t segregate

heterochromatin

dark parts of ideogram, no genetic info

euchromatin

light parts of ideogram containing genetic information

ideogram

diagrammatic representation of a chromosome, illustrating its relative size, centromere position, and characteristic banding patterns

crossing over

parental and maternal arms of tetrad overlap

recombinant chromosome

genes affected by crossing over

parental chromosomes

genes not affeected by crossing over, will be highest number in double crossovers questions

double crossovers

lowest number in double crossover questions

Thomas Hunt Morgan

determined sex-linked traits from fruit flies