Ch11 - Genetics Flashcards
What is Genetics?
The scientific study of heredity
Genes vs Alleles
Genes: factors that determine traits/ characteristics (ex. hair color)
Alleles: different forms/versions of a gene (ex. black or brown hair color)
What is a trait?
Specific characteristic that varies from individual to individual –> determined by alleles/ genes
Dominant vs. Recessive
Dominant: organism will only have this form of the gene/ this trait
Recessive: organism will only have this form if dominant allele is not present
Who came up with the Principle of Segregation and Independent Assortment?
Gregor Mendel - 1865
Segregation vs Independent Assortment
Segregation: a gene has 2 alleles –> there is an equal distribution of alleles when forming gametes
Independent Assortment: genes for different traits segregate independently of each other and do not influence each others inheritance
Define homologous
A couple of chromosomes (from both parents) that have the same size and copies of gene location
Diploid vs Haploid
Diploid: A cell with 2 sets of chromosomes (1 from each parent)
Haploid: A cel with only 1 set of chromosomes
What are the types of chromosomes? How many of each are present?
Autosomal chromosomes: 22 pairs
Allosomal/ sex chromosomes: X & Y chromosomes that determine sex
What is the purpose of Meiosis?
A reduction division to cut number of chromosomes in half to form gametes for reproduction
List of Meiosis cell cycle + what happens at each stage
- Interphase 1: DNA duplication + Cell growth
- Prophase 1: Homologous chromosomes come together –> tetrads
- Metaphase 1: Homologous chromosomes line up at the equator
- Anaphase 1: Homologous chromosomes are pulled apart by spindle fibers
- Telophase + Cytokinesis: Cytoplasm is divided, forming 2 (duplicated) haploid cells
- Prophase 2: chromatin condense to chromosomes
- Metaphase 2: Chromosomes line up at the equator
- Anaphase 2: sister chromatids are split apart
- Telophase + Cytokinesis: Cytoplasm divides, forming 4 haploid cells
What is a tetrad?
2 homologous chromosomes together
What is crossing over? When does it happen? What is the purpose? Where does it happen?
- Exchange of genes between non-sister chromatid in a tetrad
- Prophase 1
- Bring variety in the gametes
- Chiasma
What is the result of meiosis 1?
2 haploid cells w/ duplicated chromosomes
What is the result of meiosis 2?
4 haploid cells
How many gametes are formed in male & female?
Males: 4 sperm cells
Females: 1 egg & 3 polar bodies
Why are polar bodies formed?
They allow for the reduction of chromosomes while preserving the cytoplasm for 1 egg
How many combinations of zygotes are there?
2^n
n = # of paired chromosomes
What is a zygote?
First cell produced when sperm and egg are fertilized
Mitosis vs. Meiosis
Mitosis:
- Produce genetically identical cells from parents
- 1 cell division
- Results in 2 Diploid cells
- Occurs in all organisms
- Creates all somatic cells (not sex cells)
- No recombination/ crossing over
- In metaphase, chromosomes line up at equator
- In anaphase, sister chromatids separate
Meiosis
- Produce genetically diff. cells from parents
- 2 cell division
- Results in 4 haploid cells
- Occurs in only animals, plants, and fungi
- Creates only germ cells –> sperm, egg
- Involves recombination/ crossover for genetic variety
- In metaphase 1, homologous pairs line up at equator
- In anaphase 1, homologous pairs separate
What is a karyotype? What is its function?
A visual diagram containing images of all chromosomes present in a cell
- used to identify any abnormalities in the chromosome count
What is nondisjunction?
Chromosomes fail to divide properly resulting in too many or too little # of chromosomes in the final cell
Trisomy vs monosomy
Trisomy: having an additional chromosome
Monosomy: having 1 less chromosome
What is aneuploidy?
Combined term for trisomy + monosomy
- showing abnormal chromosome count
