Q&A: Chromosome & DNA Replication Flashcards
Q: How many pairs of chromosomes are found in cells in humans?
A: 23 pairs of chromosomes
Q: How many total chromosomes are found in cells in humans?
A: 46 chromosomes
Q: How many total chromosomes are found in sperm and ovum cells?
A: 23 chromosomes
Q: What type of cells are human somatic cells?
A: Diploid cells (contain 2 complete cells of chromosomes)
Q: What type of cells are gametes?
Gametes are reproductive/sex cells, such as sperm and egg. Sperm and eggs are haploid cells.
Q: What is the function of helicase?
A: Enzyme that is responsible for unwinding & separating DNA double helix into two strands during DNA replication.
Q: What is the function of DNA polymerase?
A: Enzyme that adds complimentary nucleotides to each original strand of DNA creating two new DNA strands.
Q: What is the function of ligase?
A: Ligase connects Okazaki fragments together with a phosphodiester bond.
What are the 3 Steps of DNA Replication?
- Initiation
- Elongation
- Termination
Q: Explain the process of DNA Replication.
A:
Initiation:
- DNA replication begins at origin site
- Helicase is used to break H bonds between the base pairs in DNA
- Primase lays down primer (RNA) in the 5’ to 3’ direction (this indicated to DNA polymerase where to start)
- DNA polymerase attaches to the primers
Elongation:
- DNA polymerase creates complimentary strand by matching complimentary bases
- DNA can only be build from the 5’ to 3’ direction, so the leading strand is created continuously, but the lagging strand is created in short fragments called Okazaki fragments
- Okazai fragments are glued together via ligase (via phosphodiester bond b/c DNA is nucleic acid)
Termination:
- DNA polymerase is finished
- Replication forks meet up
Explain how DNA is “involved”/condenses into a chromosome
- DNA wraps around histone proteins = nucleosome
- A bundle of nuclemosomes = chromatin
- Chromatin condenses further into a chromosome that has organized genes
T/F: A chromosome has very little genes
False, chromosomes contain 100s-1000s genes
Each gene codes for ____ protein
one
Not really, but this is good enough to know for the TEAS
Explain why each DNA copy will become shorter and shorter?
Okazaki fragments cannot be made at the end of linear DNA because there is no place for RNA primers to attache to the last okazaki fragmet, therefore, each copy becomes shorter and shorter
T/F: DNA polymerase reads DNA in the 5’ to 3’ direction, and will build in the 3’ to 5’ direction
False, DNA polymerase reads DNA in the 3’ to 5’ direction, and will build in the 5’ to 3’ direction.
