Heredity Flashcards

Flashcards for Heredity Lecture Review

Gene

A basic unit or sequence of genetic material that encodes a trait

Locus

A gene's location within a genome

Allele

A variant form of a gene

Wild type

Normal version of an allele

Mutant

An allele with an altered DNA sequence affecting a gene's phenotype

Genotype

The alleles an individual carries (e.g., Aa)

Phenotype

The set of observable characteristics in an individual resulting from the expression of genotype

Homologous chromosomes

A pair of chromosomes (1 maternal, 1 paternal) that contain the same genes in the same locations

Hemizygous

Having only one copy of a gene instead of two (e.g., sex chromosomes of males are XY)

Heterozygous

Carrying a copy of the recessive allele on one of the homologous chromosomes and a copy of the dominant allele on the other chromosome (e.g., Aa)

Homozygous

Carrying the same alleles on each homologous chromosome

Homozygous Dominant

Carries two copies of the dominant allele (e.g., BB)

Homozygous Recessive

Carries two copies of the recessive allele (e.g., bb)

Test Cross

A genetic cross between a homozygous recessive individual and an individual in question to determine the latter's genotype for a given trait

Punnett squares

Show all possible allelic combinations of gametes in a cross between two individuals with known genotypes

Law of Segregation

During Anaphase 1, homologous chromosomes segregate, resulting in haploid gametes that contain only one allele per gene

Monohybrid cross

Tests a single gene

Dihybrid cross

Tests two different genes simultaneously

Test cross generations

P1 (parental), F1 (1st generation of offspring), F2 (2nd generation of offspring)

Law of Independent Assortment

The lining up & separation of one pair of homologous chromosomes does not influence that of a different pair of homologous chromosomes

Law of Dominance

A dominant allele masks the effect of a recessive allele

Epistasis

One gene affects the phenotypic expression of an independently inherited gene

Multiple Alleles

More than two typical alleles exist for a gene

Polygenic Inheritance

Many genes interact to shape a single phenotype, often with continuous variation

Pleiotropy

Single gene controls for the expression of multiple phenotypic traits

Incomplete Dominance

There is a blending of alleles, producing a unique heterozygous phenotype

Codominance

Both alleles are completely expressed

Segregation

Pairs of alleles are separated when gametes are formed

Independent Assortment

Pairs of alleles will be sorted independently of one another when gametes are formed

Principle of Dominance

One dominant allele masks effect of recessive allele

Sex-linked genes

Genes reside on a sex chromosome

Sex-influenced genes

Genes can be affected by the sex of the individual carrying the trait

Linkage map

Uses recombination frequency to show the relative positions of genes on a chromosome

Linked genes

Reside close together on a chromosome, making them less likely to be separated by recombination during meiosis, and more likely to be inherited together

X-inactivation

During embryonic development in female mammals, one of the two X chromosomes is inactivated, forming a highly condensed chromosome (Barr body)

Aneuploidy

The occurrence of an abnormal number (extra/missing) of chromosomes that is often caused by nondisjunction

Trisomy 21 (Down syndrome)

Having three copies of chromosome 21 instead of the normal two copies

Nondisjunction

The failure of chromosomes or chromatids to separate during Mitosis/Meiosis; can result in gametes with too many or too few chromosomes

Penetrance

The proportion of individuals with a specific genotype will express the corresponding phenotype

Expressivity

The variation of a phenotype for a specific genotype

Autosomal dominant

A single copy of the mutated gene is enough to express the condition

Autosomal recessive

Two copies of the mutated gene must be present to express the condition

X-linked dominant

A single copy of the mutation of a gene on the X chromosome is enough to cause the condition in both males & females

X-linked recessive

Two copies of the mutated gene on the X chromosomes causes the condition in females; one copy will cause the condition in males

Y-linked

Genes located on the Y chromosome cause the condition/trait

Colchicine

Arrests mitosis by interfering with mitotic spindle formation; it can prevent cells from replicating and has anticancer effects

Proto-oncogenes

Stimulate normal growth; if mutated become oncogenes (cancer-causing genes)

Tumor suppressor genes

Make proteins that help control cell growth; if mutated may lead to cancer

Chromosomal aberrations

Changes in chromosome number or structure

Inversions

A chromosome segment is rearranged in the reverse of its original orientation

Deletions

A chromosome segment is missing or deleted