Genetics 210 (Exam 2)

Lethal alleles

Lethal alleles

Alleles that cause an organism to die when present in homozygous condition.

Sex-influenced inheritance

the sex influences the expression of a phenotype that is not limited to one sex or the other

Sex-limited inheritance

Expression of specific phenotype is absolutely limited to one sex

Sexual dimorphism

Differences between the sexes in secondary sexual characteristics.

Epistasis

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

Pleiotropy

A single gene having multiple effects on an individuals phenotype

Cytoplasmic inheritance

Transmission of genes that occur outside the nucleus

Endosymbiosis theory

The theory that the eukaryotic cell evolved via the engulfing of one prokaryotic cell by another.

Heteroplasmy

Presence of two or more distinct variants of DNA within the cytoplasm of a single cell.

Maternal effect

The genotype of the mother determines the phenotype of the offspring

Maternal inheritance

Genes that are inherited only from the mother (all organelles come only from the ovum).

Mendelian inheritance

the basic principles of the transmission of genetic material, including the law of segregation and the law of independent assortment

Paternal inheritance

A type of inheritance in which the organelles in the offspring cells derive from those in the father.

Paternal leakage

paternal parents provides mitochondria through sperm

DNA methylation

The addition of methyl groups to bases of DNA after DNA synthesis; may serve as a long-term control of gene expression.

Epigenetic inheritance

Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence.

Genomic imprinting

Variation in phenotype depending on whether an allele is inherited from the male or female parent.

Independent assortment

the random distribution of the pairs of genes on different chromosomes to the gametes

Nonrecombinants

An offspring whose combination of traits has not changed from the parental generation.

Recombinant

An offspring whose phenotype differs from that of the parents

Syntenic blocks

blocks of linked loci within a genome

Acrocentric

Describes a chromosome whose centromere is placed very close to one end.

Deletion

A change to a chromosome in which a fragment of the chromosome is removed.

Duplication

A change to a chromosome in which part of the chromosome is repeated

G band

A visible band that arises when eukaryotic chromosomes at prophase or metaphase are stained with the DNA dye Giemsa

Inversion

A chromosome piece reattaches to original chromosome but in reverse orientation

Metacentric

Centromere in middle of chromosome

Gene family

A group of genes with related functions

Interstitial deletion

A chromosome breaks at two locations, the central fragment is lost, and the outer pieces rejoin

Nonallelic homologous recombination

Recombination that occurs at sites within chromosomes due to the occurrence of repetitive sequences

Ortholog

Homologous genes in different species

Paralog

Genes that arise by duplication within species

pseudogene

A DNA segment very similar to a real gene but which does not yield a functional product; a gene that has become inactivated in a particular species because of mutation.

Repetitive sequences

Segments of DNA repeated multiple times in a genome

Terminal deletion

Deletion at end of chromosome

Unequal crossing-over

Misalignment of the two DNA molecules during crossing over, resulting in one DNA molecule with an insertion and the other with a deletion

Inversion heterozygote

A individual that carries one normal chromosome and a homologous chromosome with an inversion

Translocation

A fragment of one chromosome attaches to a nonhomologous chromosome.

Allodiploid

An organism that contains one set of chromosomes from two different species

Allopolyploid

A species with multiple sets of chromosomes derived from different species

Autopolyploid

Polyploidy formed within a single species

Euploid

A normal number of chromosomes

Haplodiploid

When males are haploid, females are diploid

Monosomic

A chromosomal condition in which a particular cell has only one copy of a chromosome, instead of the normal two.

Complete nondisjunction

during meiosis or mitosis, when all of the chromosomes fail to disjoin and remain in one of the two daughter cells

Mosaicism

Presence of genetically distinct cell lines in the same individual

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

Genetic transfer

The method of increasing genetic variation in prokaryotes that involves cells "grabbing" stray pieces of DNA from their environment or exchanging DNA directly with other cells

Horizontal transfer

The transfer of DNA from one cell to another by a process other than cell division, such as bacterial conjugation

Conjugation

A temporary union of two organisms for the purpose of DNA transfer.

Transduction

DNA is transferred from a donor cell to a recipient via a bacteriophage

Transfection

Transformation of bacteria with DNA extracted from a bacterial virus

Virus

A tiny, nonliving particle that invades and then reproduces inside a living cell.

Lysogenic cycle

A viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA

Lytic cycle

A viral reproductive cycle in which copies of a virus are made within a host cell, which then bursts open, releasing new viruses

Reverse transcriptase

A polymerase that catalyzes the formation of DNA using RNA as a template

Chargaff's rule

A=T and C=G