Unit 3

Heredity: the transmission of traits from one generation to another

Genetics: the scientific study of heredity and variation

Genes: units of heredity and made of segments of DNA

Gametes: genes passed to next generation via reproductive cells

Humans have: 46 chromosomes

Asexual: a single individual passes all genes onto offspring without the fusion of gametes

Clone: group of genetically identical individuals from the same parent

Sexual reproduction: two parents give rise to offspring

that have unique combinations of genes

Human somatic cells have: 23 pairs of chromosomes

karyotype: ordered display of the pairs of chromosomes from a cell

The sex chromosomes: x and Y

the remaining 22 pairs of chromosomes are: called autosomes

females: xx

Males: xy

homologous chromosomes: includes one chromosome from each parent

46 chromosomes are in two sets of 23 one from mother one from father

Fertilization: union of gametes

fertilized egg is called : zygote

The only type of human cells produced by meiosis: gametes

Results in one set of chromosomes in each gamete: Meiosis

exhibit an alternation of generations: Plants and some algae

diploid organism: called sporophyte and makes haploid spores by meiosis

spore grows by: mitosis

chromosomes duplicate before meiosis

the stages of meiosis: prophase I, metaphase I, anaphase I, telophase I and cytokinesis.

division of meiosis: prophase II, metaphase II, anaphase II, telophase II and cytokinesis.

mitosis: conserves the number of chromosome sets,producing cells that are genetically identical to the parent cell.

meiosis: reduces the number of chromosomes sets from two diploid to one haploid, producing cells that differ genetically from each other and parent cell.

mutations: changes in organism’s DNA

three mechanisms to genetic variation: Independent assortment of chromosomes, crossing over, Random fertilization.

two laws of inheritance: The law of segregation and the law of independent assortment.

Pleiotrophy: most genes have multiple phenotypic effects.

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

traits that depend on multiple genes combined with enviromental influences are called: multifactorial

phenotype: physical appearance, internal anatomy, Physiology and behavior, overall genotype

pedigree: family tree that describes interrelationships of parents and children across generations

Recessively inherited disorders: show up only in individuals homozgous for the allele

Cystic Fibrosis: most common lethal genetic disease in USA

Sickle cell disease: one out of 400 african americans

In amniocentesis: liquid bathes the fetus is removed and tested

In chorionic villus sampling (CVS): sample of placenta is removed and tested

Phenylketonuria (PKU): recessively inherited disorder that occurs in one of every 10,000 -15,000 births in the USA

A gene on the Y chromosome called SRY is responsible for: developement of the testes in an embryo

X chromosome contains: 1,100 genes

For a recessive X-linked trait to be expressed: a female needs two copies of the allele(homozygous), and a male needs only one copy (hemizygous)

In mammalian females: one of two Xchromosomes in each cell is randomly inactivated during embyonic developement

Each chromosome other then the Y chromosome: Have hundreds or thousands of genes

Linked genes: genes located on the same chromosome tend to be inherited together

Parental types: offspring with a phenotype matching one of the parental phenotypes

recombinant types: offspring with nonparental phenotypes

linkage map: genetic map of chromosome based on recombination frequencies

large scale chromosomal alterations in humans and other mammals often lead to: spontaneous miscarriages, or lead to disorders

Plants tolerate: genetic changes better than animals

nondisjunction: pairs of homologous chromosomes do not seperate normally during meiosis

polyploidy: condition in which an organism has more then two complete sets of chromosomes

polyploidy is more common in: plants

Breakage of chromosome can lead to four types of changes in chromosome structure: Deletion, Duplication, Inversion reverses, translocation

Cri du chat syndrome: causes severly intellectually disabled, cat like cry and usually die in infancy or early childhood

imprinted genes: critical for embryonic developement

extranulear genes are found in: the cytoplasm

Extranuclear genes are inherited: maternally

Heredity is encoded in: DNA

DNA is copied during: DNA replication