EXAM 2 Flashcards
What are the stages of the cell cycle, and what is the function of each stage?
G1 (cell growth), S (DNA replication), G2 (preparation for mitosis), and M phase (mitosis).
How does DNA replication occur?
DNA replication is semi-conservative
meaning each new DNA molecule has one old strand and one new strand
what is base pairing?
Base pairing involves A-T and G-C pairing to create a complementary strand
Define chromosome.
A chromosome is a DNA molecule with genetic material
Define gene.
A DNA sequence coding for a trait
Define allele.
An allele is a gene variant
Define DNA
a molecule that contains the genetic code that is unique to every individual
Define genome.
The genome is all genetic material
Define sister chromatids.
sister chromatids are duplicated chromosomes
Define homologous pairs.
homologous pairs are chromosome pairs from each parent
What is the difference between autosomes and sex chromosomes?
Autosomes are non-sex chromosomes (22 pairs in humans), while sex chromosomes determine gender (XX or XY)
What is mitosis, and which cells undergo it?
Mitosis is cell division that produces identical daughter cells, occurring in somatic (body) cells for growth and repair
Name three ways mutations are introduced into DNA.
- DNA replication errors
- Environmental factors (e.g., UV radiation),
- Chemicals (mutagens).
What are three types of mutations?
- Substitution (base change)
- Insertion (extra base added)
- Deletion (base removed)
What are potential consequences of a mutation?
- nonfunctional proteins
- genetic disorders
- beneficial changes, affecting cell functions
How do cell cycle checkpoints prevent most cells from becoming cancerous?
Checkpoints verify DNA integrity
verify proper cell function. Damaged cells are stopped from dividing, preventing mutations from passing on.
Why do tumor cells display unique characteristics?
Tumor cells bypass checkpoints
divide uncontrollably
can obtain mutations that enable rapid growth and spread
What role does meiosis play in the human life cycle?
Meiosis produces gametes (sperm and eggs)
splits chromosome number for sexual reproduction and genetic diversity
What is the structure and role of homologous chromosomes in meiosis?
Homologous chromosomes pair up during meiosis, each containing different alleles. They allow for genetic variation through crossing over
How does crossing over occur, and why is it important?
Crossing over is the exchange of genetic material between homologous chromosomes, increasing genetic diversity
Describe random assortment in meiosis and its result
Random assortment is the independent separation of chromosomes, leading to varied genetic combinations in gametes
What are the differences between mitosis and meiosis?
Mitosis creates identical cells, while meiosis creates genetically unique gametes.
Meiosis includes two divisions, reducing chromosome number
Describe complete dominance with examples.
Complete dominance shows one trait (e.g., brown eyes)
Define incomplete dominance with examples
incomplete dominance blends traits (e.g., pink flowers from red and white parents).
What is a carrier in autosomal recessive diseases?
A carrier has one copy of a recessive allele but does not show symptoms. Example: a carrier for cystic fibrosis (CF)
How can Punnett squares predict genotypes in sex-linked conditions?
Punnett squares show the likelihood of offspring inheriting X-linked traits, using XX/XY to represent female/male chromosomes
How long does the cell cycle take to complete?
Approximately 21-27 hours
G1 phase (8-10 hours)
S phase (6-8 hours)
G2 phase (6-8 hours)
mitosis (1 hour)
What are the stages of interphase, and what happens in each?
G1 (growth), S (DNA replication), and G2 (preparation for mitosis). G0 is a resting phase
What happens in prophase?
Chromosomes condense and the nuclear envelope breaks down.
What happens in metaphase?
Chromosomes align in the middle of the cell on the metaphase plate
What is anaphase?
Sister chromatids separate and are pulled to opposite sides of the cell
What happens during telophase?
Nuclear membranes reform around each chromosome set, and chromosomes begin to decondense
What is cytokinesis?
The cell membrane pinches in, dividing the cytoplasm to form two identical cells, each with a complete set of chromosomes
What are sister chromatids?
Identical copies of a chromosome joined at the centromere, formed during S phase
How are homologous chromosomes different from sister chromatids?
Homologous chromosomes are similar but non-identical pairs, one from each parent, carrying the same types of genes
What role do centrosomes play in mitosis?
They organize spindle fibers that pull chromosomes to opposite cell poles
Describe the chromosome structure in prophase.
Chromosomes condense into X-shaped structures, each made up of two sister chromatids
When does DNA replication occur, and what is its result?
DNA replication occurs during S phase, resulting in each chromosome having two identical sister chromatids
How does the cell ensure each new cell gets identical DNA?
Sister chromatids separate during anaphase, each new cell receiving a complete set of chromosomes
How do chromosomes align during metaphase?
They can line up in any order on the metaphase plate
Does having more chromosome pairs change the process of mitosis?
No, only more spindle fibers are required, but the phases of mitosis remain the same
