AP Bio: Meiosis + Genetics

Meiosis

(genetics) cell division that produces reproductive cells in sexually reproducing organisms

Pluripotent

Stem cells that are capable of developing into most, but not all, of the body's cell types

Totipotent

Stem cells with the potential to differentiate into any type of cell.

Haploid

term used to refer to a cell that contains only a single set of chromosomes and therefore only a single set of genes

Diploid

(genetics) an organism or cell having two sets of chromosomes or twice the haploid number

Synapsis

the side by side pairing of homologous maternal and paternal chromosomes at the start of meiosis

Tetrads

the paired chromosomes consisting of four chromatids

Sister Chromatid

replicated form of a chromosome that will separate during Anaphase

Crossing Over

the interchange of sections between pairing homologous chromosomes during the prophase of meiosis

Somatic Cells

any cell other than a gamete, has 46 chromosomes, body cells

Gametes

sex cells

Zygote

a fertilized egg

Genotype

Letter combination of alleles, Ex. BB, Bb, bb

Phenotype

Physical trait of an organism. Ex. brown hair

Homozygous

Having the same alleles. Ex. BB or bb

Heterozygous

Having both a dominant and recessive allele. Bb

Gene

A segment of DNA on a chromosome that codes for a specific trait

allele

one of two alternate forms of a gene that can have the same locus on homologous chromosomes and are responsible for alternative traits. Ex. Allele for blue & brown eyes.

Law of Segregation

Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete

Law of Independent Assortment

states that allele pairs separate independently during the formation of gametes

Monohybrid Cross

hybridization using a single trait with two alleles (as in Mendel's experiments with garden peas)

Dihybrid Cross

hybridization using two traits with two alleles each

Incomplete Dominance

creates a blended phenotype; one allele is not completely dominant over the other

Codominance

a condition in which both alleles for a gene are fully expressed

Multiple Alleles

three or more forms of a gene that code for a single trait (such as blood types)

Epistasis

One gene masks the expression of a different gene for a different trait. Ex. Hair has more than one set of genes which cause different color, texture, etc.

Pleiotropy

A single gene having multiple effects on an individuals phenotype (more than one phenotypic expression). Skin color has different degrees of pigmentation.

Linked Genes

genes located on the same chromosome that tend to be inherited together in genetic crosses

Sex Linked Inheritance

Traits located on the sex cells. EX: Colorblindness, hemophilia.

Nondisjunction

failure of chromosomes to separate during Anaphase; gametes end up with wrong number of chromosomes

Aneuploidy

an abnormality involving a chromosome number (one chromosome set is incomplete)(causes down sydrome and turners syndrome)

Polyploidy

condition in which an organism has extra sets of chromosomes

Point Mutations

changes in a DNA sequence caused by substitution of one nucleotide for another

karyotype

picture of the chromosomal makeup of a somatic cell in an individual or species (including the number and arrangement and size and structure of the chromosomes)

homologous chromosomes

chromosomes that have the same sequence of genes, that have the same structured, and that pair during meisosis

Autosomes

non-sex chromosomes

P Generation

parental generation, the first two individuals that mate in a genetic cross

f1 Generation

the first offspring from a cross of two varieties in the parental (P) generation

f2 Generation

the second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation

Pedigree

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

Recessive Disorders

No functional information is inherited on both chromosomes, harmful. Ex. cystic Fibrosis, Tay Sachs & Sickle Cell

Tay-Sachs

recessive, lipid build up, causes fat build up in brain. death by 2

Klinefelter Syndrome

(XXY) syndrome in males that is characterized by small testes and long legs and enlarged breasts and reduced sperm production and mental retardation

Sickle cell anemia

A human genetic disease of red blood cells caused by the substitution of a single amino acid in the hemoglobin protein

Hemophilia

sex-linked recessive disorder defined by the absence of one or more proteins required for blood clotting

Huntington's disease

genetic disorder that causes progressive deterioration of brain cells. Dominant allele. symptoms do not appear until the age of 30 or so

Dominant Disorders

One dominant allele is present for these disorders. Ex. Achondroplasia, Huntington's disease

Cystic fibrosis

a human genetic disorder caused by a recessive allele for a chloride channel protein; characterized by an excessive secretion of mucus; fatal if untreated (4% whites are carriers - most common lethal genetic disease)

Albinism

Autosomal Recessive , a hereditary condition characterized by a partial or total lack of melanin pigment (particularly in the eyes, skin, and hair)

Penetrance

The percent of individuals with a particular genotype that actually displays the phenotype associated with the genotype.

Down Syndrome

a congenital disorder caused by having an extra 21st chromosome

Turners Syndrome

(XO) condition seen in individuals carrying single X chromosome but no other sex chromosome

Deletion

removes a chromosomal segment

Duplication

repeats a segment of a chromosome

Inversion

Chromosome segment is flipped

Translocation

moves a segment from one chromosome to another