GN 311 Module 1

transmission genetics

focus on individual genetic makeup and how genes are passed to the next generation

molecular genetics

focus on gene structure, organization, and function

population genetics and evolution

focus on gropu of genes found in the population

biotechnology/genomics

focus on how genetic tools and information can be used to cure diseases and solve problems

criteria for each functional chromosome

centromere, telomere, and one origin of replication (sequence where replication is initiated)

the number of chromosomes is equal to...

the number of centromeres (chromosomes can have 1 or 2 chromatids)

submetacentric

metacentric

telocentric

acrocentric

locus vs allele

Locus- specific location on a chromosome
Allele- different forms of genes that occur on the same loci

autosomes

same chromosomes and number of homologs between sexes

sex chromosomes

different chromosomes or different number of homologs between sexes

ploidy number vs total number of chromosomes

ploidy # - number of sets of chromosomes
total # of chromosomes - number of chromosomes in a somatic cell during G0 or G1

#s of chromosomes and chromatids during mitosis stages

mitosis interphase

90% of cell life spent in interphase; during this time each chromosome is replicated, after replication, chromosomes consist of 2 identical sister chromatids (held together at center by centromere)

mitosis prophase

Chromatin in the nucleus condenses to form chromosomes. The pairs of centrioles move to opposite sides of the nucleus. Spindle fibers form a bridge between the ends of the cell. The nuclear envelope breaks down.

mitosis metaphase

The chromosomes line up across the center of the cell. Each chromosome attaches to a spindle fiber at its centromere.

mitosis anaphase

third phase of mitosis where sister chromatids separate into individual chromosomes and are moved apart into two groups near the poles of the spindle, phase ends when chromosomes stop moving

mitosis telophase

The chromosomes begin to stretch out and lose their rodlike appearance. A new nuclear envelope forms around each region of chromosomes.

reductional division (meiosis I)

- # of chromosomes in daughter cells = 1/2 number in original cell, one of each homologous pair is in each duaghter cell
- separation of homologs

equational division (meiosis II)

- # of chromosomes at beginning & end of division cycle is the same, but daughter cells only have one chromatid
- separation of chromatids

# of chromosomes and chromatids during meiosis phases

significance of meiosis

results in variablity!

cohesin

holds siter chromatids together in mitosis and meiosis
acts as chiasmata in meiosis to hold homologs (diff forms of protein in meiosis & mitosis)

shugoshin

protects cohesin @ centromere in anaphase I of meiosis, but is degraded by anaphase ii, allows homologs to separate in anaphase i but keeps siter chromatids together

nondisjunction in meiosis results in...

unbalanced gametes

mendel's observations

- hereditary determinants are particulate in nature
- each individual has 2 of these particles (one from each parent)
- when unlike particles meet in the same individual, one is dominant and the other is recessive, and individual looks like dominant characteristics
- during gamete formation, particles segregate randomle and equally to the gametes so that each gamete contains one of the pairs of alleles
- gametes unite randomly in fertilization without regard as to which allele is present

mendel's law of random segregation

two alleles of a locus do not blend or fuse, but segregate randomly into the gametes so that half of the gametes contain one allele and half contain the other allele

mendel's law of independent assortment

- segregation of alleles at one locus is independent of segregation of alleles at another locus
- alleles of diff genes migrate into gametes without influencing each other

multiplication/product rule

- if two events occur independently of each other, the probability of them occurring simultaneously is the product of the probabilities of each event occurring by itself

addition rule

the probability of two or more mutually exclusive events that cannot happen at the same time is the sum of their probability

chi square analysis

determines how well observed data fits unexpected results from a genetic hypothesis

critical value

number we compare to calculated chi-square value in order to decide whether to reject out hypothesis

XX/XO (O = no chromosome)

sexes have diff number of chromosomes

XX/XY Lygaeus mode of sex determination

sexes have same number of chromosomes, but one pair doesn't look homologous

heterogametic sex

The sex with two different sex chromosomes; a human male

homogametic sex

the sex with identical types of sex chromosomes; the human female

hemizygous

A gene present on the X chromosome that is expressed in males in both the recessive and dominant condition

pseudoautosomal region

regions of homology betwen X and Y can allow for some crosisng over

SRY gene

codes for testis determining factor (TDF) which triggers undifferentiated gonadal tissue to form testis

Turner syndrome genotype

XO (missing chromosome, can live normally but may have issues with reproduction or sterility)

Klinefelter syndrome

XXY (can be problematic, fertility issues)

XXX genotype

CAN influence phenotype, X activation not 100%, female with variable expression

XYY genotype

male, nondisjunction of Y, very few genes/less noticeable phenotypic issues

Lyon hypothesis for dosage compensation

Inactivation of an X chromosome occurs randomly in somatic cells at some point in development. Once inactivated, all progeny cells have the same X inactivated --> inactivated X is called a Barr body

how many Barr bodies on:
- normal female
- normal male
- turner individual
- klinefelter individual

Norm female: 1
Norm male: 0
turner: 0
klinefelter: 1

X linked trait

gene on X chromosome

CVS: chorionic villus sampling diagnostic

- as early as week 6
- chorion is made by fetus' genotype
- can be done by going through uterus

diagnostic testing

identifies a genetic condition/disease that is/can make a person ill. results help in disorder treatment/management

predictive and pre-symptompatic genetic testing

finds genetic variations that increase person's chance of developing specific diseases
type of genetic testing may help provide info about person's risk of developing disorder, can help in decisions about lifestyle/healthcare

carrier testing

tells people if they carry a genetic change that can cause a disease
carriers usually show no signs of disorder, but can pass on genetic variation to children, who may develop disorder

pharmacogenetic testing

gives info about how certain meds are processed in body
type of testing can help healthcare provider choose meds that work best w/ person's genetic makeup

research genetic testing

helps scientists learn more ab how genes contribute to health & disease, as well as develop gene-based treatments
sometimes results do not help research participant, but may benefit others in future by helping researchers expand their understanding of human body

genetic information nondiscrimination act (GINA)

health insurance companies cannot decrease coverage or increased rates based on results of genetic tests
employers cannot discriminate based on results
health ins companies nor employers can require genetic testing

monozygotic twins & dizygotic twins pedigree symbol

consanguineous mating

mating between relatives

pedigree assumption

assume individuals w/o parental info are NOT carriers unless evidence indicates otherwise

complete dominance

one allelic form expressed (dominant form) one is not seen (recessive form)

incomplete/partial dominance

phenotype of F1 is intermediate to that of 2 parents
only 1 gene produced
varying amounts of gene produce create the phenotype

codominance

heterozygote expresses both alleles as distinct gene products
same phenotypic ratio as incomplete dominance 1:2:1

lethal alleles

Mutated genes that are capable of causing death.

recessive lethal - 1 copies of alleles required to result in death of individua;
dominant allele - death occurs in individ has only 1 copy of allele (difficult to observe dominant lethal mutation, only see if it does not kill indiv b4 birth)

multiple alleles

2+ forms of same gene capable of producing different phenotypes
diploid organism has 2 alleles at any locus, but may be many alleels in population

allele series

multiple alleles present w/dominance hierarchy
e.g. W>X>Y>Z, W = most dominant

ABO blood group & multiple alleles

3 alleles: IA, IB, IO
4 phenotypes: A, B, AB, O
IA = IB = codominant, both dominant to IO

Blood typing (genotype, antigen type, and antibodies)

penetrance

percent of individuals of a given genotype that show some degree of expression of that genotype

expressivity

range of expression of a genotype

factors influencing phenotype for a given genotype

modifying genes, mprinting, environmental effects (i.e. temperature, nutrition, light, etc)

pleiotropic effects

one gene has an effect on several seemingly unrelated aspects of an individual's phenotype (one gene affects the phenotype of several unrelated traits)

phenocopy

an environmental agent mimics a genetic condition, causes symptoms NOT genetic change

epistasis

- expression of alleles at one locus masks or modifies the expression of other alleles at another locus --> multiple genotypes = same phenotype
- interaction between 2 diff genes, NOT interaction between alleles at one locus
- gene that masks the action of another is EPISTATIC to the masked gene

single recessive epistasis

- homozygous recessive condition at one locus masks or modifies the expression of alleles at a 2nd locus
- e.g. aa = albino mouse no matter what is at the B locus; A allele present = agouti IF there is a B allele present or black if bb is present
- 9:3:4(3+1), A_B_:A_bb:(aaB_ + aabb)

modified dihybrid ratio

gropu different genotype classes together to determine type of epistasis

single dominant epistasis

- dominant allele at one locus masks or modifies the expression of alleles at a second locus
- if A is epistatic to B and b, then A_ results in a particular phenotype no matter what is at the B/b locus
- 9:3:3:1, A_B_:A_bb:aaB_:aabb

duplicate recessive epistasis

- identical phenotypes produced by both homozygous recessive genotypes, so a different phenotype is produced ONLY if there is at least one dominant allele at each locus
- genotype aa__ and __bb result in same phenotype, no matter genotype of other locus
- 9:3:3:1, A_B_:A_bb:aaB_:aabb

duplicate dominant epistasis

- having at least one dominant allele at either locus results in the same phenotype. diff phenotype produced when homozygous recessive occurs at both loci (duplicate/redundant genes)
- genotype A__ and __B results in the same phenotype, no matter genotype of other locus
- 15:1, (9A_B_ + 3A_bb + 3aaB_) + aabb

Dominant/recessive interaction (dom and rec epistasis)

- dominant at one locus and/or homozygous recessive at the other locus results in same phenotype
- A_____ and aabb result in the same phenotype
- 13:3, (9A_B_ + 3A_bb + 1aabb): 3aaB_

Bombay phenotype

phenotypically type O, genetically due to lack of H substance, not genotype IOIO

epistasis vs dominance

epistasis: interaction between products of different genes
dominance: interaction between different alleles at a particular gene

complementation tests

mutations in same gene --> complementation does not occur, mutations = alleles of same locus

mutations in diff genes --> complementation does occur, mutations are NOT alleles

progeny = mutant, mutations in same gene

non-complementation, mutations are alleles of the same locus

progeny = normal (wild type), mutations in different genes

complementation

sex-limited

autosomal characteristic that is expressed in only one sex or the other

sex-influenced

autosomal trait that can be expressed in either sex but is more frequent in one sex than the other

genetic maternal effect

phenotype of offspring is determined by mother's genotype and not its own genotype

extranuclear/cytoplasmic inheritance

genes located on mitochondria or chloroplast DNA and generally

characteristics of cytoplasmic traits

- present in males and females
- uniparental inheritance (usually mother to all offspring)
- reciprocal crosses give different results
- show extensive phenotypic variation even within a family

endosymbiotic theory for organelle origin

- based on observation that mitochondria and chloroplast DNA and apparatus associated with their DNA functions is similar to that of bacteria
- many antibiotic resistance genes found in bacteria have been seen in DNA of mitochondria and chloroplasts
- possible origin of organelles: they were distinct bacteria-like organisms that became incorporated into primitive eukaryotic cells
- symbiotic relationship developed through evolution so that each became dependent on each other to survive

genomic imprinting

expression of a gene depends on whether it is inherited from maternal or paternal genome

epigenetics

heritable changes in gene expression without changes in DNA sequence
genomic imprinting is one form of epigenetics