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
- Independent Assortment
- Random Fertilization
- 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)