Unit 7 Biology

Heredity

passing of characteristics from parents to offspring

Genetics

science that focuses on heredity

Alleles

different versions of a gene

Dominant trait

expressed form of a trait ex: T

Recessive trait

trait not expressed if dominant allele is present ex: t

Genotype

genetic makeup of an organism ex: TT or Tt

Phenotype

physical appearance of an organism

Homozygous

two alleles present are the same ex: TT or tt

Heterozygous

two alleles present are different ex: Tt

Punnet Square

diagram that predicts outcomes of genetic cross

Carrier

person has one copy of the gene but is not usually seen in their phenotype

Meiosis

how sperm and egg cells are produced with half the number of chromosomes

Fertilization

union of haploid (n) sperm and egg

produces a zygote (fertilized egg)

2n

diploid number of body cells in body cells

n

haploid cell

Karyotypes

images of chromosomes that can show if chromosomes are repeated or deleted

S phase

part of interphase where DNA replication occurs

must happen before both meiosis and mitosis

Crossing over

during prophase 1 of meiosis 1 where genetic material is exchanged between homologous pairs leading to increased variation of offspring

Codominance

A condition in which both alleles for a gene are fully expressed (the black and white chicken)

Incomplete Dominance

one allele is not fully dominant over the other (red

Multiple alleles

three or more forms of a gene that code for a single trait (blood types A

Sex-linked traits

Traits controlled by genes located on sex chromosomes.

Pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family.

Autosomes

Any chromosome that is not a sex chromosome (#1-22)

Autosomal trait

determined by genes found on one of the first 22 pairs of chromosomes

sex chromosomes

X and Y chromosomes.

Which gender is affected more frequently with a sex linked trait?

males

Gametes

reproductive cells

Somatic cells

body cells

Meiosis I

Homologous chromosomes separate

Meiosis II

sister chromatids separate

Prophase I

Crossing over occurs

What gamete combinations would be produced from the genotype AaBB?

AB or aB