Genetics Chapter 2

Chromosomes

Structures within living cells that contain the genetic material (both coding and non-coding). The term also can refer to either a dyad or a monad

What are chromosomes composed of?

DNA and proteins

In eukaryotes, the DNA-protein is called…

Chromatin

What can chromatin also contain?

Non-coding RNAs

What are the main differences between eukaryotes and prokaryotes?

1) Prokaryotes have a DNA genome, but do not have chromatin or non-coding RNA

2) Prokaryotes do not contain a nucleus

3) Prokaryotes are not compartmentalized

What kind of genome do prokaryotes have?

Double-stranded DNA

The two copies of a replicated chromosome are called…

Sister chromatids

A single chromatid is called…

Monad

A pair of sister chromatids is called…

Dyad

What are sister chromatids held together by?

Centromere

What happens to sister chromatids upon mitosis (cell division)?

They separate into daughter cells

What are separated sister chromatids called?

Daughter chromosomes

A bacteria is an example of…

Prokaryote

What is the job of a cytologist?

Cytologists study chromosomes to spot abnormalities and help with diagnoses

What is the job of a cytogeneticist?

Cytogeneticists study the composition of chromosomes

Most eukaryotic species are…

Diploid

How many sets of chromosomes do humans have?

23 sets

What is the difference between a male and female karyotype?

A male karyotype contains an X and a Y, while a female karyotype contains two X’s

What is the process of preparing a karyotype?

1) Treat the cells with a chemical that causes them to undergo mitosis

2) Treat the cells with a hypotonic solution that causes them to swell

3) Expose the cells to chemical dyes that bind to the chromosomes and stain them

What are homologous chromosomes?

Homologous chromosomes are almost identical - they have the same loci (location) and are the same size - but there’s a chance to have a difference in the genetic composition in the form of alternative alleles

What is an allele?

A different version of a gene

What are the three types of genotypes?

1) X/X: Homozygous for the dominant allele

2) X/x: Heterozygous

3) x/x: Homozygous for the recessive allele

What is the importance of cell division?

1) Allows for asexual reproduction performed by unicellular organisms, which include bacteria, amoeba, and yeast

2) Achieving multicellularity

How do prokaryotes reproduce?

Asexually by binary fission

Mitosis in eukaryotes require…

A replication and sorting process

In actively dividing cells, G1, S, and G2 are collectively known as…

Cell cycle

In G1 phase…

The cell prepares to divide

In S phase…

Chromosomes are replicated

In G2 phase…

The cell accumulates the materials needed for nuclear and cell division

In M phase…

The cell undergoes mitosis

Centromere

DNA that’s hidden beneath the kinetochore proteins

Kinetochore

Proteins attached to the centromere

What is the primary purpose of mitosis?

Distribute the replicated chromosomes to the daughter cells

Humans have how many pairs of sister chromatids

46 pairs

What are the five phases of mitosis?

1) Prophase

2) Prometaphase

3) Metaphase

4) Anaphase

5) Telophase

What is cytokinesis?

Happens at the end of mitosis where:

In animals, the formation of a cleavage furrow

In plants, the formation of a cell plate

What are spindle apparatuses?

Protein structures that help separate out chromosomes from metaphase into anaphase

The three types of spindle fibers include…

1) Aster microtubules

2) Polar microtubules

3) Kinetochore tubules

Where are centrosomes located?

On the sides of the cell

A pair of ______ at right angles to each other is found within each centrosome

Centrioles

Aster microtubles

Found in the centrosomes which help with positioning of the centrosome apparatuses at the two poles. This is to ensure that they’re as far apart as they are relative to the cell

Polar microtubules

Help push the poles away from each other. Wouldn’t have chromosomes separated otherwise

Kinetochore microtubules

Attach to the kinetochore, and are responsible for helping physically rip apart the chromosomes from one another

In eukaryotes, the type of cell division that is responsible for the production of gametes is…

Meiosis

Synapsis is the process in which…

Homologous chromosomes recognize each other and begin to align themselves in prophase I