DNA Replication & Transcription
What is transcribed from DNA?
mRNA
What disorder is caused by trisomy 21?
Down syndrome
Where does translation occur?
Ribosome
How many daughter cells are produced in mitosis?
Two
Who is known as the father of genetics?
Gregor Mendel
Which enzyme unwinds the DNA double helix?
Helicase
What is Turner syndrome?
A disorder where females have only one X chromosome.
What molecule carries amino acids to the ribosome?
tRNA
How many daughter cells are produced in meiosis?
Four
What is the phenotypic ratio in a monohybrid cross Aa x Aa?
3:1
What is the role of primase in replication?
It synthesizes RNA primers
Which disorder is caused by an extra X chromosome in males?
Klinefelter syndrome
What is the start codon?
AUG
In which phase do homologous chromosomes separate?
Meiosis I
What is a genotype?
The combination of alleles an organism has
In eukaryotes, what modification occurs to pre-mRNA before it leaves the nucleus?
Splicing (removing introns) and adding a cap & poly-A tail
What is a karyotype?
A picture of an individual’s chromosomes.
What are codons?
Triplets of nucleotides that code for amino acids
What is the main difference between anaphase in mitosis and meiosis II?
Mitosis: sister chromatids separate; Meiosis II: sister chromatids separate again
What does the law of independent assortment state?
Alleles for different traits segregate independently.
Explain the difference between transcription in prokaryotes and eukaryotes.
Prokaryotes transcribe mRNA directly and it can be translated immediately; eukaryotes produce pre-mRNA that requires processing (splicing, 5’ cap, poly-A tail) before translation.
Explain how nondisjunction can lead to chromosomal disorders and give an example.
Nondisjunction is the failure of chromosomes to separate properly during meiosis, leading to an abnormal number of chromosomes (e.g., trisomy 21 → Down syndrome).
Describe the roles of the A, P, and E sites on the ribosome during translation.
A site = entry for tRNA; P site = holds tRNA with growing polypeptide; E site = exit site for empty tRNA.
Explain how crossing over contributes to genetic variation.
During prophase I of meiosis, homologous chromosomes exchange segments, creating new allele combinations in gametes.
What is a dihybrid cross and what phenotypic ratio is expected for a cross AaBb x AaBb?
A dihybrid cross studies two traits at once; expected phenotypic ratio = 9:3:3:1