BIO 151 Module 3

Heredity

the transmission of traits from one generation to the next

Variation

differences in appearance that offspring show from parents and sibling

Alleles

different versions of the same gene

Locus

the location of a gene on a chromosome

Karyotype

ordered display of the pairs of chromosomes from a metaphase cell

Diploid

2 of each chromosomes

Homologous chromosomes

a pair of chromosomes that contains the same genetic information

Autosome

Chromosomes 1-22

Somatic cell

every cell in the body except the gametes

Polyploidy

a condition in which an organism has more than two complete sets of chromosomes

Fertilization

the fusion of two gametes (egg and sperm)

Zygote

fertilized egg

Meiosis

the process of producing a haploid cell

G1 phase

growth, prepare for DNA replication

S phase

DNA replication

G2 phase

growth, prepare for meiosis

M phase

meiosis

Meiosis reduces…

the number of chromosome sets from diploid to haploid by going through 2 meiotic cell divisions

Meiosis I

homologous chromosomes separate

Meiosis II

sister chromatids separate

Interphase

chromosomes duplicate to create sister chromatids

Synaptonemal complex

links the homologous chromosomes together and facilitates crossing over during prophase I

Chiasmata

the structures formed during crossing over, cause genetic variation

Prophase I

each chromosome pairs with its homologous and crossing over occurs

Metaphase I

pairs of homologs line up on the metaphase plate with one chromosome facing each pole

Anaphase I

pairs of homologous chromosomes separate (sister chromatids remain attached at the centromere)

Telophase I and cytokinesis

two haploid daughter cells are produced

Prophase II

spindle forms, chromosomes move to center of cell

Metaphase II

sister chromatids align on metaphase plate, kinetochores are attached to each centrosome

Anaphase II

sister chromatids are pulled apart

Telophase II and cytokinesis

produces four daughter cells, each with a haploid set of chromosomes

At what stage and how do chromosomes undergo independent assortment?

Meiosis I, metaphase alignment

Mendel

studied the genetic inheritance of different traits in the pea plant

P

parental gene

F1

first filial generation

F2

second filial generation

True breeding organisms

posses traits that are inherited unchanged by all offspring produced by self fertilization

Law of segregation

only one copy of each chromosome is passed on to the offspring from each parent

Monohybrid

heterozygous for one trait

Dihybrid

heterozygous for 2 traits and shows dominant phenotype for both traits

Codominance

both alleles are expressed equally (equally dominant) in the phenotype (roan cows)

Incomplete dominance

neither allele is fully dominant, resulting in a heterozygous phenotype that is a blend of the two traits (pink flowers)

multiple alles

more than two allelic forms (ex: blood type)

Pleiotropy

genes that have multiple phenotypic effects

Polygenic inheritance

traits that are determined by two or more genes

Epistasis

a gene at one locus alters the phenotypic expression of a gene at a second locus

Multifactoral

traits that depend on multiple genes combined with environmental influences

Amniocentesis

Amniotic fluid is withdrawn

Chorionic villus smapling

suction tube inserted through cervix to collect fetal cells without amniotic fluid

Deletion

removes a chromosomal segment

Duplication

repeats a chromosomal segment

Inversion

reverses orientation of a chromosomal segment

Translocation

moves a chromosomal segment from one chromosome to another

Nondisjunction

pairs of homologous chromosomes do not separate normally during meiosis

Aneuploidy

extra or missing chromosomes in the gamete

Klinefelter syndrome

extra chromosome in a male, producing XXY individuals

Turner syndrome

monosomy X, produces X0 females

XXX females

healthy, no unusual physical features

Down syndrome

aneuploid condition that results from three copies of chromosome 21

Thomas Hunt Morgan

studied genetics using fruit flies

wild type

normal phenotype

mutant

traits alternative to normal phenotype

X-linked gene

characteristics unrelated to sex

Y-linked gene

sex determination

Linked genes tend to be inherited together because…

they are located near each other on the same chromosome, they do not follow the law of independent assortment

Recombination frequency

can determine the relative distance between 2 genes

linkage map

shows the relative location of genes along a chromosome