Which stage in Meiosis the Crossing over takes place?

Prophase I

List 3 different points which leads to variation in the offspring during sexual reproduction

1. Independent Assortment
2. Random Fertilization
3. Crossing Over

How many possible combination can arise from independent assortment alone?

8 million

How many daughter cells are produced at the end of Meiosis

4 daughter cells

A cell containing a single set of chromosomes

Haploid

Which step of Meiosis resemble Mitosis

Meiosis II

These are units of heredity that are made up of segments of DNA

Genes

Cells that undergo Meiosis

Gametes (Sperm and Egg)

One parent produces genetically identical offspring by mitosis

Asexual reproduction

Two parents give rise to offspring that have unique combinations of genes inherited from the two parents

Sexual reproduction

Any cell other than a gamete

Somatic cells

An ordered display of the pairs of chromosomes from a cell

Karyotype

Two chromosomes in each pair

Homologous chromosomes

Name the sex chromosomes

X and Y

The 22 pair of chromosomes that do not determine sex

Autosomes

Two haploid daughter cells with replicated chromosomes

Reductional division

Four haploid daughter cells with unreplicated chromosomes

Equational division

• More than 90% of the time required for meiosis
• Chromosomes begin to condense
• Homologous chromosomes loosely pair up, aligned gene by gene (Synapsis)
• Non sister chromatids exchange DNA segments (Crossing over)
• Each pair of chromosomes forms a tetrad

Prophase I

• Tetrads line up at the equator of the cell

Metaphase I

• Pairs of homologous chromosomes separate
• One chromosome moves toward each pole

Anaphase I

• A spindle apparatus forms
• Chromosomes move toward the equator of the cell

Prophase II

• Sister chromatids are arranged at the equator of the cell

Metaphase II

• Sister chromatids separate and move toward opposite poles

Anaphase II

Chromosomes which combine genes inherited from each parent

Recombinant chromosomes

The fusion of two gametes produces how many combinations

70 trillion

Plants that produce offspring of the same variety when they self-pollinate

True-breeding

Mating two contrasting, true-breeding varieties

Hybridization

The true-breeding parents

P generation

The hybrid offspring of the P generation

F1 generation

F1 individuals self-pollinate producing

F2 generation

Individuals carry pairs of hereditary "elements" for each trait. These pairs separate for reproduction and reform pairs in offspring

Mendel's First Law = Principle of Segregation

Alternative versions of a gene

Alleles

A heritable factor

Gene

An organism with two identical alleles for a character

Homozygous

An organism that has two different alleles for a gene

Heterozygous

Determines the organism's appearance

Dominant allele

Has no noticeable effect on appearance

Recessive allele

Physical appearance

Phenotype

Genetic makeup

Genotype

What is the genotypic ratio from a monohybrid cross

1:2:1

What is the phenotypic ratio from a monohybrid cross

3:1

Used to tell the genotype of an individual with the dominant phenotype

Testcross

What is the phenotypic ratio from an dihybrid cross

9:3:3:1

When phenotypes of the heterozygote and dominant homozygote are identical

Complete (True) dominance

The phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties

Incomplete dominance

Two dominant alleles affect the phenotype in separate, distinguishable ways

Codominance

• Albinism
• Cystic fibrosis
• Phenylketonuria
• Sickle - cell disease
• Tay-Sachs disease

Recessively Inherited Disorders

• Achondroplasia
• Huntington's Disease
• Polydactyly

Dominantly Inherited Disorders

Most genes have multiple phenotypic effects

Pleiotropy

The liquid that bathes the fetus is removed and tested

Amniocentesis

A sample of the placenta is removed and tested

Chorionic Villus Sampling (CVS)