vocab terms

chromosome

a structure containing genetic information in the form of genes

chromatin

the material that makes up eukaryotic chromosomes; consists of a DNA molecule complexed with the histone proteins (ch. 19)

chromatid

one double-stranded DNA copy of a replicated chromosome with its associated proteins

sister chromatids

two attached, double-stranded DNA copies of a replicated chromosome

• happens when chromosomes are replicated

• identical genetic material

• become independent when separated during mitosis

centromere

a specialized region of a chromosome where sister chromatids are most closely joined to each other 

kinetochores

the structures on sister chromatids where microtubules attach

microtubule-organizing center

any structure that organizes microtubules

centrosome

the microtubule-organizing center in animals and certain plants and fungi

centrioles

cylindrical structures consisting of microtubule triplets, located inside animal centrosomes

unreplicated chromosome

a chromosome that consists of one double-helical molecule of DNA packaged w/proteins for compactness

replicated chromosome

a chromosome after DNA replication

homologous chromosomes (homologs)

have the same genes in the same position and are the same size + shape.

non-sister chromatids

chromatids on different members of a homologous chromosome pair

bivalent

homologous replicated chromosomes that are joined togehter during prophase I and metaphase I of meisosis

sex chromosome

chromosome associated w/an individual’s sex

autosome

any chromosome other than a sex chromosomeh

haploid number

n = # of different types of chromosomes in a cell

diploid number

2n = number of chromosomes present in a diploid cell

ploidy

number of each type of chromosome present

haploid

having one of each type of chromosome (n)

diploid

having 2 of each type of chromosome (2n)

polyploid

having more than 2 of each type of chromosome

sex linkage

a gene is located on a sex chromosome

linkage

2 or more genes are on the same chromosome

incomplete dominance

intermediate phenotype (heterozygotes)

codominance

phenotypes of both alleles (heterozygotes)

multiple allelism

more than 2 common alleles for a locus in a population

polymorphism

more than 1 phenotype associated w/a single gene in a population

pleiotropy

a single gene affects many traits

gene-gene interaction

phenotype associated w/an allele depends on which alleles of another gene are present

gene-environment interaction

phenotype is influenced by the environment experienced by individuals with the same genotype

polygenic inheritance

a trait which exhibits continuous variation rather than coming in distinct types

autosomal inheritance

the patters of inheritance on any gene not on a se chromosome. 

• “standard” patterns of inheritance

gene

hereditary factor that influences a particular trait

allele

particular form of gene

genotype

a listing of the alleles of a particular gene in an individual

phenotype

observable traits

homozygous

two of the same allele

heterozygous

two diff alleles

dominant allele

an allele that produces its phenotype in heterozygous and homozygous genotypes

recessive allele

only in homozygous phenotypes

pure line

individuals w/the same phenotype, that, when crossed, alwyas produce offspring w/the same phenotype

hybrid

offspring from crosses between homozygous parents w/diff genotypes

reciprocal cross

a cross whciht he phenotypes of male and female are reversed compared w/a prior cross

testcross

cross of a homozygous recessive and an individual w/the dominant phenotype but unknown

x-linked

gene located on x chromosome

y-linked

gene located on y chromosome

silent

change in nucleotide sequence that does not change the amino acid

• no change in phenotype

missense

change in nucleotide sequence that changes the amino acid

• may be beneficial, neutral, or deleterious

nonsense

change in nucleotide sequence that causes an early stop codon

• leads to a shortened polypeptide (usually deleterious)

frameshift

addition/deletion of a nucleotide

• reading frame is shifted, altering the menaing of all subsequent codons

• almost always deleterious