Bio 311 midterm study

Gene

A hereditary unit of information

Wild type

The most prevalent phenotype in a population under natural conditions

Mutant

a deviation to the wild-type phenotype as a result from an allelic change in DNA

Gene locus

The position of a gene on the chromosome

Allele

One of two (or more) versions of a gene that differs in sequence and exists at the same loci

Genotype

The combination of alleles for any gene

Phenotype

Observable characteristics, as determined by the genotype

Dominant

The phenotype observed in heterozygous individuals (i.e. genotype includes both allele variants) (does not equal wild type)

Recessive

The phenotype observed only in individuals that are homozygous for the recessive allele (does not equal mutant)

How many traits did Gregor Mendel observe and what were they?

7 traits: pea color, pea shape, pos color pod shape, flower color, plant height, position of flowering shoot

Gregor Mendel tested traits with only ____ phenotypes

2, "dominant" and "recessive"

What determines if one allele is dominant over the other?

Proteins produced in each of the alleles

When is wild-type phenotype produced?

Produced when an organism has two copies of wild-type allele, or when one copy is sufficient to meet the protein requirements

Loss of function

Significant decrease or complete loss of functional gene product (A type of mutation in which the altered gene product lacks the molecular function of the wild-type gene)

Gain of function

Gene product acquires a new function (mutation) or expression increased above wild-type activity

Incomplete Dominance

Heterozygous individuals display intermediate phenotypes between either homozygous type

Codominance

Results when there is detectable expression of both alleles in the heterozygotes

haploinsufficient

For a particular gene, one functioning copy is not enough for a wildtype phenotype.

Single letter nomenclature

Mutant phenotype or recessive allele if mutant is unknown

Capital letter nomenclature

dominant allele

Lower case nomenclature

recessive allele

Slashes nomenclature

Indicates genes on homologous chromosomes

Semicolons nomenclature

Indicates genes on non-homologous chromosomes

What organism did Gregor Mendel study?

Garden peas!

How did Gregor Mendel examine traits

Through crossing and selfing

Discontinuous trait

phenotypes that are expressed in clear-cut variations

True Breeding

Organisms that, when reproducing, create offspring of all the same variety.

Monohybrid cross

A cross between individuals that involves one pair of contrasting traits

Equal Segregation

In a heterozygote (Aa), half of the products of meiosis will carry one allele (A) and the other half will carry the other allele (a).

Test cross

Determine if phenotypically dominant individual is homozygous dominant or heterozygous, testers are homozygous recessive

Who is in chromosomal theory of inheretance

Sutton, Boveri and Morgan

What did they propose

Looked at chromosome separation during meiosis under microscope, proposed mendels particle where chromosomes

Parts of a chromosome

telomere, P arm (shorter), Q arm (longer), centromere

Metacentric

centromere in middle

acrocentric

centromere close to end

telocentric

centromere at end

Homogametic

Matching sex chromosome (XX)

Heterogametic

No matching pair (XY)

How can heterogametic form a synaptomenal complex

Pseudoautosomal regions

propositus

In a human pedigree, the person who first came to the attention of the geneticist (usually has a disease)

Mendel's second law of independent assortment

inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes

Independent assortment results in gametes which are ____ recombinant

50%

Lethal alleles

Lethality occurs when two copies of a mutant allele are inherited

Penetrance

The % of individuals with a mutation that show the phenotype (some individuals with mutant phenotype will not show the mutant phenotype)

Expressivity

the degree to which a trait is expressed

Why would individuals with the same mutation not show exactly the same phenotype

Environment, Other genes, Fine distinction of mutant phenotype

If any gene in a pathway is mutated what happens to wild-type phenotype?

Phenotype is no longer wild type

Beadle and Tatum

Investigated genetic control of cellular chemistry (Neurospora

Ascospores are transferred to culture tubes of ______ medium (sugar, salt, water)

complete

Complementation test

method of discovering whether two mutations are in the same or separate genes

Complement

alleles of different genes

Fail to complement

alleles of the same gene

synthetic

genes on the same chromosome

Do linked genes follow the law of independent assortment?

No!

Linked

A b / a b

Unlinked

A/a ; B/b

Unsure

A/a . B/b

cis conformation

Same

trans conformation

Different

Chiasmata

Cross shaped structures that form during meiosis when two dyads form a tetrad (bivalent) early stages of prophase

Frequency of Recombinants is directly related to _______ between genes

distance, larger distance = higher chance of crossing over

Karyotype:

an individual's complete set of chromosomes.

Karyotypes generally remain ____ within a species

constant

Related species usually have _____ karyotype

different

Chromosomal ______ can result in all classes of chromosomal rearrangements

breakage

Abnormal _____ at repeated sequences can also produce rearrangements

crossing over

Translocation

Change to a chromosome in which a fragment of one chromosome attaches to a nonhomologous chromosome.

Rearrangements can impact phenotypes or even viability by affecting _________

Gene balance

Severity of effect can depend if individual is ________ or _______ for rearranged chromosomes

Homozygous or heterozygous

Recombinants only occur at _________ regions

homologous, no recombinant can occur within a deletion loop

Tandem duplications

repeats of a chromosomal region that lie adjacent to each other, either in the same order or in reverse order

nontandem duplications (dispersed)

two or more copies of a region that are not adjacent to each other and may lie far apart on the same chromosome or on different chromosomes

Entire genes duplicate

produce multigene families

Gene families produce

gene superfamilies

Lowest level, exons ______ or __________

Duplicate, shuffle

If there is breakage between a gene, can it change gene function

No

Inversion

A chromosomal mutation involving the removal of a chromosome segment, its rotation through l80 degrees, and its reinsertion in the same location.

When is inversion loop formed

During meiosis

Inversion loop

a loop formed by meiotic pairing of homologs in an inversion heterozygote

prototroph

able to synthesize all the nutrients required for their growth

auxotroph

unable to synthesize all of the vital nutrients (requires addition of organic compounds)

Horizontal gene transfer

Movement/exchange of genetic info without sexual reproduction or cell division

Conjugation

Direct contact between bacterial cells and DNA is transferred from donor to the recipient (small circular plasmid/ a part of the bacterial genome)

Transformation

Picking up free DNA from the environment/ a dead bacterial cell

Transduction

Virus mediates transfer to DNA from donor bacterial cell to the recipient cell

The F plasmid (or fertility factor) enables the information of a pilus and the attachment of F____ cells to F___ cells

+ to -

Fertility (F) factor

a plasmid that gives the bacterial cell the ability to produce a pilus

Does the recipient cell usually become a F+ donor?

No, pilus is not very stable so its rare

Does F+ donor become F- when it donates plasmid?

No, remains F+ donor because plasmid donated is replicated

Hfr strain

a bacterial strain in which the F factor is integrated into the chromosome, Hfr strain contains F factor in its gnome

Hfr x F- cross

Hfr is able to transfer DNA attached to F factor into recipient cell

What happens to linear DNA that remains in the cell in HfrxF-

it is recycled by cell

DNA replication and transfer begins were in Hfr x F-?

Where the F factor was integrated, transfer starts at the origin of transfer

Exconjugant

Cell that contains fragment of donor DNA; has participated in conjugation

Hfr x F- have _______ genotype

opposite

F- is usually _______

auxotrophic

When is interrupted mating used for

To determine order of bacterial genes

Can F plasmid integrate at different sites and in different orientations?

yes

Recombination takes place between a ________ genome and an ________ genome

complete, incomplete

Exogenote

partial genome