AP Bio Unit 4: meiosis, heredity and genetic diversity

Haploid

A cell containing only one complete set of chromosomes

Diploid

A cell containing 2 complete sets of chromosomes

Gamete

A haploid reproductive cell that is formed by meiosis

Daughter cell

New cells produced from the division of a single parents cell, inheriting genetic material and organelles

Homologous chromosomes

A pair of chromosomes of the same length, centromere position and staining pattern that passes genes for the same characters at corresponding loci

Sister chromatids

2 identical DNA copies of a single duplicated chromosome joined at the centromere

Crossing over

The exchange of genetic material between homologous chromosomes during prophase 1 of meiosis, resulting in new combinations of alleles and increasing genetic diversity

Synapsis

In prophase 1 where homologous pair up precisely, which allows for genetic exchange through crossing over between non sister chromatids, creating new allele combinations and increasing genetic diversity

Chiasmata

Occur at points of crossing over, hold homologs together, allowing them to align properly at metaphase plate

Recombination

Exchange of genetic material between homologous chromosomes, ensures that each generation has a unique genetic makeup

Random assortment

On maternal chromosome and one paternal chromosome and their orientation is random

Kinetochore

Located at the entry mere of each sister chromatids, serves as the attachment site for spindle microtubules during cell division, link spindles motor to chromosomes

Microtubule

Crucial role in chromosome movement, attach to chromosomes and shorten, pull chromosomes toward spindle, esssential for accurate chromosome segregation, ensuring each daughter cell receives the correct genetic material

Fertilization

The union of a sperm and egg cell, essential for sexual reproduction

DNA

Nucleic acid molecule, capable of replication and determines the inherited structure of cells proteins, genetic material that organisms inherit from their parents

Mendels law of segregation

Chromosomes carry alleles, if homologous they carry alleles for the same trait, when chromosomes are separated into daughter cells, the alleles for each trait are also separated and allows for genetic variation in gametes

Mendels law of independent assortment

2 or more alleles assort independently of each other, 1 trait it not automatically inherited with another trait

Dominant allele

Trait that is expressed in the phenotype

Recessive allele

Variant of a gene that must be inherited from both parents to be expressed

Homozygous

Two identical alleles for a specific gene

Heterozygous

Two different alleles for a particular gene

Zygote

A diploid cell produced by the union of haploid gametes during fertilization

Monohybird

Study of a single trait

Test cross

Genetic technique used to determine the genotype of an organism that exhibits a dominant trait

Dihybrid

The study of two trait

Autosomal

Refers to the chromosomes, that are not sex chromosomes

Sex-linked

Genes located on the sex chromosomes, primarily the X chromosome carry many genes not related to the sex of the offspring sex

Genetically linked traits

Characteristics that tend to be inherited together because the genes that are responsible for the traits are located near each other on the same chromosome

Pedigree

Method to study the inheritance of traits in families

Genotype

Describes the collection of genes, letter make up of genes

Phenotype

The physical traits

Codominance

Heterozygous have both traits equally expressed , phenotype that displays characteristics of both alleles distinctly

Incomplete dominance

Where neither allele is completely dominant over the other, heterozygous have their own phenotype different from their parents

Pleiotrophy

Where a single gene influences multiple phenotypic traits

Map distance

The measurement of genetic distance between genes on a chromosome, based on recombination frequencies

Chloroplasts DNA/ inheritance

From the mother

Phenotypic plasticity

The ability of an organism to change it phenotype in response to environmental conditions, allows organisms to adapt to varying environments

No disjunction

Chromosomal mishap during meiosis where chromosomes fail to separate properly, cause gametes with abnormal chromosome numbers

Aneuploidy

Where cells have an abnormal number of chromosomes, may have an extra chromosome or one less chromosome

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape

Meiosis

Produces 4 genetically diverse daughter cells, reduces chromosome sets from diploid to haploid, involved two division cycle, essential for sexual reproduction

Sexual reproduction advantages

Genetic variation, dispersal and dormancy

Sexual reproduction disadvantage

Requires both male and female partners, takes more energy/time

Asexual reproduction advantages

Efficiency, faster, takes less energy

Asexual reproduction disadvantages

Less genetic variation, can’t accommodate changes in environment

Polygenic inheritance

Where a single phenotype is influences by multiple genes

Deletion

Where a fragment of the chromosome is lost, results in chromosome missing genes, causes by errors in meiosis

Duplication

Where a segment of a chromosome is duplicated

Inversion

Where a fragment of the chromosome reattaches in reverse orientation

Translocation

Where a fragment of one chromosome breaks off and attaches to a non homologous chromosome, affects gene expression