Genetics exam 2 quizlet PDF

Preview

Summary

Download Genetics exam 2 quizlet PDF

Description

Genetics Terms (Exam 2) Study online at quizlet.com/_84ks2a 1.

Novel phenotypes

observed when the interaction between two loci yields new phenotypes and modified Mendelian dihybrid ratios

17.

recombinant gametes

gametes with new combinations of alleles (non parental); occurs at lower frequency

2.

sex-influenced inheritance

the phenotypic expression is conditioned by the sex of the individual; autosomal trait; NOT X-linked

18.

the lesser chance of crossing over

3.

sex-limited inheritance

the phenotypic expression is limited to only one of the two sexes

The shorter the distances between nonsister chromatids...

4.

epigenetic change

Variations in physical or physiological traits that are potentially heritable but are not caused by changes in DNA base sequences and may be reversible

19.

The longer the distances between nonsister chromatids...

the higher chance of crossing over

5.

genomic imprinting

a chemical modification in DNA that may inactivate a gene in a reversible way

20.

theoretical limit of recombination

50%

conditional alleles

express a wild type (normal) phenotype under certain conditions and a mutant phenotype under restrictive conditions; not reversible (Ex. temperature-sensitive mutations, dominant lethal alleles)

21.

Double crossover

cross over then cross back (two events); lowest frequency

22.

Coefficient if coincidence (C)

Obs. DCO/Expected DCO

23.

equation for interference

I=1-C

24.

Interference

a crossover event in one region of the chromosome may reduce the probability of crossover events in nearby regions

25.

positive interference

Fewer double crossovers than expected

26.

no interference

Observed DCO = Expected DCO (I = 0)

27.

complete interference

when no double crossovers occur

28.

negative interference

more double crossovers than expected

29.

Reproduction

the production of new individuals

30.

sex

the combining of genes from two individuals to generate new genetic combinations

31.

conjugation

In bacteria, the direct transfer of DNA between two cells that are temporarily joined through a sex pilus; unidirectional (from F+ to F-)

32.

F+ cell

-the donor -has the fertility factor (F factor; plasmid) that confers the ability to donate part of its DNA during conjugation

33.

F- cell

-recipient cell - becomes F+ after the donor transfers the F factor to it

6.

7.

Discontinuous variation

involves discrete phenotypic categories; usually results from the expression of a single locus

8.

continuous variation

results from additive phenotypes

9.

quantitative inheritance

(aka polygenic); the phenotype reults from the expression of multiple genes (Ex. skin color, body size)

10.

normal distribution

# of phenotypic categories = # of max. possible additive alleles + 1

11.

Meristic traits

are polygenic but show a discrete number of phenotypes, often influenced by multiple genetic/environmental factors, and are counted in whole numbers (Ex. # of flower petals)

12.

Threshold traits

Polygenic but discontinuous: the trait is either present or absent

13.

Mendelian independent assortment

gamete formation when two heterozygous gene pairs are on separate chromosomes; gametes occur w/ equal probability

14.

linkage

gamete formation when 2 heterozygous gene pairs are on the same chromosome

15.

crossing over

exchange of chromosomal material between homologous chromosomes during by breakage and reunion during prophase 1 of meiosis

16.

nonrecombinant gametes

gametes that contain only original combinations of alleles present in the parents; occurs at high frequency

34.

plasmids

extrachromosomal circular DNA molecules that may carry beneficial genes; uncommon; aren't necessary for normal function

35.

r-determinant

genes that confer the cell resistance to antibiotics

36.

RTF segment

resistance transfer factor (necessary for plasmid replication)

37.

transformation

a hertiable change in a cell or organism brought by exogenous DNA; may come from: - another cell (conjunction) - environment (free exogenous DNA) - a virus

38.

Bacteriophage

A virus that infects bacteria

39.

Phage T4

like all DNA viruses, it contains viral DNA encapsulated inside a protein structure unlike eukaryotic viruses, the entire virus does not penetrate the cell; the phage injects its DNA into the bacterial cell and the protein components remain outside

40.

lysogenic cycle

the phage DNA becomes incorporated into the host cell's DNA and becomes a prophage

41.

prophage

phage DNA that is integrated into a specific site of the host cell's chromosome (lysogeny)

42.

transduction

bacterial DNA transfer mediated by phages

43.

endosymbiotic theory

mitochondria and chloroplasts derived from prokaryotes that entered eukayotic cells and became adapted to perform specific cellular functions...