AP Bio Unit 5 (Heredity) Vocab

Heredity

The transmission of traits from one generation to the next through genetic information.

Genes

Segments of DNA that act as instructions to build proteins and RNA, forming the blueprint that determines traits like cell function and eye color.

Mutations

Any personal change in an organism’s DNA or nucleic acid sequence, which could lead to effects on an organism’s traits.

Homologous Chromosomes

A pair of chromosomes (same size, length, centromere position) that carry the same genetic information.

Asexual Reproduction

A single parent produces genetically identical offspring without the fusion of gametes via mitosis.

Sexual Reproduction

A biological process where two parents combine their genetic material through gametes to create genetically unique offspring.

Karyotype

A display of chromosome pairs ordered by size and length.

Somatic Cell

Body cells that are diploid (2 sets of each chromosome).

Gametic Cell

Sex cells that are haploid (1 set of each chromosome).

Diploid

2 complete sets of each chromosome.

Haploid

1 complete set of each chromosome.

Autosome

Chromosomes that do not determine sex.

Sex Chromosomes

X (Eggs) & Y (Sperm); These determine sex.

Life Cycle

Sequence of stages in the reproductive history of an organism from conception to its own reproduction.

Zygote

Formed when a sperm cell fertilizes an egg.

Genetics

The study of heredity & heredity variation.

Clones

Offspring that are exact copies of the parent.

Meiosis

A process that creates haploid gametes cells in sexually reproducing diploid organisms.

Synapsis

Homologous chromosomes pair up and physically connect to each other to form a tetrad

Tetrad

2 homologous chromosomes paired together during Prophase I

Chiasmata

The physical points where crossing over occur. They hold homologous chromosomes together and ensure proper alignment and separation of homologous chromosomes.

Crossing Over

Produces recombinant chromosomes due to exchange of genetic material during Prophase I.

Independent Assortment

Chromosomes are randomly oriented along the metaphase plate during Metaphase I. Each can orient with either material or paternal chromosomes closer to a given pole.

Interphase

Cell goes through G1, S (DNA copied), and G2.

Prophase I

Synapsis (Homologous chromosomes pair up and physically connect to form a tetrad).

Metaphase I

Independent orientation (Tetrads line up at the metaphase plate).

Anaphase I

Homologous pairs separate (sister chromatids still attached).

Telophase I & Cytokinesis

Nuclei & cytoplasm divides. There is now a haploid set of chromosomes in each daughter cell.

Prophase II

Mitotic spindle forms. There is NO crossing over.

Metaphase II

Chromosomes line up at the metaphase plate. The chromatids are all unique due to crossing over in Meiosis I.

Anaphase II

Sister chromatids separate and move towards opposite poles.

Telophase II & Cytokinesis

4 genetically unique haploid daughter cells. Nuclei reappears.

True Breeding

Organisms that produce offspring of the same variety over many generations of self pollination.

P Generation

True-breeding parental generation.

F1 Generation

First filial hybrid offspring of P generation.

F2 Generation

Second filial offspring of the F1 generation.

Punnett Squares

Diagrams used to predict the allele combinations of offspring from a cross with known genetic compositions.

Monohybrid Cross

A cross between the F1 hybrids.

Dihybrid Cross

A cross between F1 dihybrids.

Phenotype

An organism’s appearance, which is determined by the genotype.

The Multiplication Rule

The probability that two or more independent events will occur together in some specific combinations.

Law of Segregation

The two alleles for the same trait separate during gamete formation and end up in different gametes.

Law of Independent Assortment

Genes for one trait are not inherited with genes of another trait.

The Addition Rule

The probability that two or more mutually exclusive events will occur.

Recessive

An allele that’s effects are hidden by a dominant allele and are only expressed when no dominant alleles are present.

Alleles

Alternative versions of a gene.

Heterozygous

An organism has two different alleles for a gene.

Genotype

The genetic makeup (alleles) of an organism.

Dominant

An allele that is expressed in the phenotype when at least one copy is present.

Homozygous

An organism that has a pair of identical alleles for a character (Dominant/Recessive).

Pedigrees

Family trees that give a visual of inheritance patterns of particular traits.

Incomplete Dominance

Neither allele is fully dominant, and the phenotype is a mix of those of the parental generation.

Polygenic Inheritance

The effect of two or more genes acting on a single phenotype.

Multiple Alleles

Genes that exist in forms with more than two alleles.

Epistasis

The phenotypic expression of a gene at one locus affects a gene at another locus.

X-Linked

Genes found on the x-chromosome.

Codominance

Two alleles that affect phenotype are both expressed.

Y-Linked

Genes specifically found on the y-chromosome. There are less genes on the y-chromosomes, so fewer disorders.

Hemizygous

When a male has an x-linked recessive allele (As males only have 1 x-chromosome, and therefore inherit the recessive trait).

Barr Body

Because females have 2 x-chromosomes, most of the x-chromosome in each cell become inactive and condenses into this, which helps to regulate gene dosage.

Recombinants

Offspring with genotypes that are different from the parents.

Linkage Map

Genetic map that is based on recombination frequencies.

Chi Square

A form of statistical analysis used to compare the actual results (observed) with the expected results.

Phenotypic Plasticity

Individuals with the same genotype exhibit different phenotypes in different environments.

Nondisjunction

Chromosomes fail to separate properly in Meiosis I or Meiosis II.