Meiosis and Genetics Lecture Notes

Flashcards covering meiosis phases, chromosome counts, cellular reproduction, and Mendelian as well as non-Mendelian inheritance patterns.

How many homologous chromosome pairs do humans have?

$$23$$

How many total chromosomes do humans have?

$$46$$

What is a somatic cell?

A normal body cell

What are gametic cells (gametes)?

Sexual reproductive cells

What are haploid cells?

$1n$, essentially has half the number of chromosomes that a diploid cell has. When $2$ haploid cells join they create $46$ chromosomes.

What is the difference between gametic and haploid cells?

Gamete cells are the only type of haploid cells, so sperm is a gamete cell making it a haploid cell as well.

What type of cell has $2$ chromosomes per type of chromosomes, and is homologous?

Diploid cells

What is syngamy?

The fusion of $2$ gametes for reproduction.

What diploid cell is a fertilized egg?

Zygote

What is an allele?

A variation of a gene

What is loci or locus?

The location of a gene or allele in a chromosome

What are X and Y?

Sex cells

What is the term for when a mistake in meiosis occurs?

Monosomy

What causes a chromosome to become "missing"?

non disjunction

What is a tetrad?

A pair of homologous chromosomes

What happens in alternation of generations?

A reproductive life cycle in plants and algae where an organism goes between a multicellular haploid stage and a multicellular diploid stage.

What is meiosis in short terms?

The process of reduction division

How many daughter gametes are produced from meiosis?

$$4$$

How does meiosis begin?

It begins by duplicating the DNA but dividing twice

What duplicates during the S phase of meiosis 1?

Chromosomes

Where does crossing over occur?

The tetrad

What happens in prophase 1?

The DNA from the mother and father, which were previously separate chromosomes, cross over and come together.

What happens in metaphase 1?

The chromosomes line up at the equator in an independent assortment.

What happens in anaphase 1?

The homologous chromosomes separate

What happens in telophase 1?

The cells begin to pull apart, and there will be $2$ diploid daughter cells

What happens in prophase 2?

Spindle fibers form to separate sister chromatids

What happens in metaphase 2?

Chromosomes line up in the center

What happens in anaphase 2?

The sister chromatids are pulled apart. Once seperated they are called chromosomes.

What happens in telophase 2?

The cells begin to split apart into $4$ haploid daughter cells, as the $2$ daughter cells form, meiosis 1 splits into $2$ daughter cells each.

What is a dominant allele?

One allele that is enough for a certain phenotype to be expressed. The other allele is repressed.

What is a recessive allele?

Two alleles are required for a certain phenotype to be expressed.

What is a phenotype?

The physical expression of genes

What is a genotype?

The genetic information/specific alleles.

What is an example of a phenotype?

Brown hair

What is an example of a genotype?

BB

What is true breeding?

The crossing of two homozygous organisms resulting in offspring of the same pheno/genotype

What is a monohybrid cross?

The cross of two heterozygous organisms for two different alleles

What ratio is a monohybrid cross usually?

$1:2:1$ for genotype ratio and $3:1$ for phenotypic ratio.

What is a dihybrid cross?

A cross of $2$ organisms that are heterozygous for two different alleles.

What ratio do dihybrid crosses have?

$$9:3:3:1$$

What is incomplete dominance?

The two phenotypes encoded the alleles that are “blended together. ”

What is an example of incomplete dominance?

A flower has one red allele and one white allele so the flower is pink

What is codominance?

Both phenotypes are encoded by the alleles and are expressed in different areas, like spots or patches

What is an example of codominance?

AB blood type, a flower has one red allele and one white allele so the flower has white and red petals.

What is pleiotropy?

An allele that only controls one phenotype, but that phenotype cause effects on other phenotypes.

What is an example of pleiotropy?

Sickle cell anemia only controls red blood cells, but it can cause kidney failure.

What is epistasis?

One allele alters the phenotypic expression of a completely separate allele.

What is an example of epistasis?

In labs there are gene that control fur colors. However there is an allele that partially inhibits pigment production in the fur, causing blonde labs.

What is polygenetic inheritance?

What multiple alleles control a single phenotype

What is an example of polygenetic inheritance?

Eye color, height, skin color

What is an example of sex-linked trait inheritance?

Calico cats