BIO 311 Exam 1

common characteristics of model organisms

-short generation time

-production of numerous progeny

-carry out controlled genetic crosses

-numerous genetic variants

DNA +histones

chromatin

haploid

cell that contains 1 copy of every chromosome

N=2

diploid

cell that contains 2 copies of every chromosome

2N=4

which phases make up interphase

G1, S, G2

mitosis (definition)

separation of sister chromatids into different cells

cytokinesis

division of cytoplasm/physical serparation of cells

mitosis phases in order

interphase

prophase

prometaphase

metaphase

anaphase

telophase

cytokinesis

prophase

-chromosomes condense

-centromeres form the mitotic spindle and move into position on opposite sides of the cell

-sister chromatids are held together by cohesion at the centromere

-each chromosome possesses 3 chromatids

prometaphase

-nuclear membrane breaks down

-spindle microtubules attach to chromatids

metaphase

-chromosomes line up at metaphase place

-chromosomes are maximally condensed at this stage

anaphase

-sister chromatids separate and move towards opposite poles (this is done by the protein seperase)

telophase

-chromosomes arrive at spindle poles

-nuclear membrane reforms

-chromosomes go back to relaxed state

mitosis produces ______ cells that are genetically ______ to each other and the cell that gave rise to them

2;identical

meiosis

the production of haploid gametes (sperm and egg cells)

fertilization

the fusion of haploid gametes

interphase

DNA synthesis and chromosome replication phase

meiosis I

separation of homologous chromosome pairs, and the reduction of chromosome numbers by HALF

meiosis II

separation of sister chromatids, also know as equational division and the chromosome number stays the SAME

prophase I

-synapsis: close pairing of homologous chromosome

tetrad

closely associated four-sister chromatids of two homologous chromosomes

crossing over

exchange of genetic info between non-sister chromatids

metaphase I

random alignment of homologous pairs of chromosomes along the metaphase plate

anaphase I

-homologous chromosome pairs separate and move towards opposite poles

-random distribution of chromosomes into two newly divided cells

-cytoplasm divides

prophase II

the chromosomes recondense

metaphase II

individual chromosomes line up on the equatorial plate

anaphase II

sister chromatids separate and move towards opposite poles

telophase II

chromosomes arrive at the spindle poles and the cytoplasm divides

cytokinesis following meiosis II

-nuclear membrane reforms

-FOUR haploid gamete cells form

gene

an inherited factor (region of DNA) that helps determine a characteristic

allele

one of two or more alternative forms of a gene

locus

specific place on a chromosome occupied by an allele

genotype

set of alleles possessed by an individual organism

heterozygote

an individual organism possessing two different alleles at a locus

homozygote

an individual organism possessing two of the same alleles at a locus

phenotype (trait)

the appearance or manifestation of a characteristic

characteristic

an attribute or feature possessed by an organism

monohybrid cross

a cross between two parents that differ in a single characteristic

capital letter=

dominant allele

lowercase letter=

recessive allele

dihybrid cross

crosses involving two different traits

females make _____ gametes, males make _______ gametes

larger;smaller

females have ______ X chromosomes and males have ________

2;1

females are the ________ sex

homogametic

males are the ________sex

heterogametic

in drosophilia, 2N=

8

trisomic

2n+1

monosomic

2n-1

SRY

-male determining gene

-located on the Y chromosome

-DNA binding protein that promotes transcription of genes that are important for testes development

androgen-insensitivity syndrome

-XY individuals that have testes and produces testosterone, but haves a defective androgen receptor

-inability to make sperm or development of female secondary sexual characteristics

-inherited from mothers (on the X chromosome)

dosage compensation

equalizes the amount of protein produced by the x chromosome in males vs. females

dosage compensation in drosophilia:

males have DNA binding proteins that _______ the activity of genes on the x chromosome

doubles

dosage compensation in placental mammels:

females ________ one of their x chromosomes, which forms as ________

inactivates; barr body

barr body

inactive x chromosomes found in female cells

pedigree

-pictorial representation of a family history

-a family tree that outlines the inheritance of one or more characteristics

proband

the person from whom the pedigree is initiated

autosomal recessive traits

-appear equally in males and females

-tend to skip generations

-more likely to appear among progeny of related parents

autosomal dominant traits

-appear equally in males and females

-unaffected persons do NOT transmit the trait

-affected persons must have at least one affected parent

x-linked recessive traits

-affected male does not pass it on to their sons

-but can pass the allele to a daughter, who is unaffected/ becomes a carrier and can then pass it onto their sons

-appear more frequently in males

x-linked dominant traits

-do not skip generations

-affected males pass the trait on to ALL DAUGHTERS and NO SONS

-affected females (if heterozygous) pass the trait on to about 1/2 of sons/daughters

y-linked traits

-appear only in males

-all male offspring of an affected male are affected

dizygotic twins

2 eggs fertilized with two different sperm (genetically distinct)

monozygotic twins

single egg fertilized by a single sperm, followed by splitting of the embryo during early development (genetically identical)

concordant

both members of a twin pair have a trait

discordant

only one member of the pair have a trait

concordance

percentage of twin pairs that are concordant for a trait

dominance is determined by looking at the _______

heterozygotes

complete dominance

-a relationship in which one allele is completely dominant over another

-heterozygote resembles the homozygous parent

incomplete dominance

-situation in which one allele is not completely dominant over another allele

-red and white flowers make pink flowers

codominance

-heterozygote displays the phenotypes of both homozygotes (both alleles must be expressed)

dominance describes interactions between alleles at ________

the same locus

dominance only affects ________

phenotype (does NOT affect the way genes are inherited)

penetrance

the percentage of individuals having a particular genotype that express the expected phenotype

expressivity

the degree to which a character is expressed

incomplete penetrance

genotype does not always produce the expected phenotype

variable expressivity

variation in the degree to which a trait is expressed

lethal alleles

-causes death at an early stage of development, and so some genotypes may not appear among the progeny

-affects the mendelian genotypic and phenotypic ratios in progeny

gene interaction

effects of genes at one locus depend on the presence of genes at another locus

epistasis

one gene masks the effect of another gene

epistatic gene

the gene that does the masking

hypostatic gene

the gene whose effect is masked

recessive epistasis

the epistatic gene is recessive and thus only masks when there are two copies of the epistatic gene

dominant epistasis

only a single copy of the epistatic allele is required to mask the phenotype of the hypostatic gene

duplicate recessive epistasis

two recessive alleles at either of two loci are capable of suppressing a phenotype

complementation test

test that determines whether mutations are at the same locus or not

sex-influenced characteristics

-autosomal genes that are expressed differently in males vs. females

-higher penetrance in one of the sexes

sex-limited characteristics

autosomal gene only expressed in one sex

continuous characteristics (quantitative traits)

-exhibit continuous distribution of phenotypes

-phenotype is usually determined by interaction between many genes (polygenic)

pleiotropy

one gene affects multiple characteristics