Genetics Flashcards
7 cards from real MCAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Genetics flashcards as text
During meiosis I, homologous chromosomes separate. This division reduces the chromosome number from:
Answer: Diploid (2n) to haploid (n)
Meiosis I is the reductional division where homologous chromosome pairs separate, halving the chromosome number from diploid (2n) to haploid (n) in each resulting cell.
Phenylketonuria (PKU) is caused by a deficiency of which enzyme?
Answer: Phenylalanine hydroxylase
PKU results from a loss-of-function mutation in phenylalanine hydroxylase, which normally converts phenylalanine to tyrosine; deficiency leads to phenylalanine accumulation and neurotoxic metabolite production.
An affected male with an X-linked recessive disorder has children with an unaffected, non-carrier female. What proportion of his daughters will be carriers?
Answer: 100% — all daughters will be carriers
An affected male (X^a Y) passes his X^a chromosome to every daughter; since the mother provides only normal X alleles, all daughters will be obligate carriers (X^a X^N).
During pre-mRNA splicing, which sequences are removed to produce mature mRNA?
Answer: Introns (intervening sequences)
Introns are non-coding intervening sequences excised from pre-mRNA by the spliceosome; the remaining exons are ligated together to form the mature mRNA that is translated.
In PCR (polymerase chain reaction), which step separates the double-stranded DNA template into single strands?
Answer: Denaturation — high temperature breaks hydrogen bonds between base pairs
Denaturation (typically at ~94–98°C) disrupts the hydrogen bonds between complementary base pairs, unwinding the double helix into two single-stranded templates for subsequent primer annealing.
In CRISPR-Cas9 gene editing, the guide RNA (gRNA) functions to:
Answer: Direct the Cas9 endonuclease to a specific genomic sequence via complementary base pairing
The guide RNA contains a spacer sequence complementary to the target genomic DNA, directing Cas9 to the precise location where it introduces a double-strand break.
Mendel's Law of Independent Assortment states that:
Answer: Alleles of different genes segregate independently during gamete formation
The Law of Independent Assortment states that alleles for different genes on non-homologous chromosomes sort into gametes independently of one another, producing random combinations.