Life Cycle & Ploidy
What process reduces chromosome number by half to produce gametes?
Meiosis
A cell with 46 chromosomes and an X and Y is from a ___.
Diploid male
How many daughter cells are produced by mitosis? (include ploidy)
2 identical diploid cells
What was the F₂ phenotypic ratio in Mendel’s monohybrid cross?
3:1
A trait seen in every generation is likely ___.
Autosomal Dominant
What is the ploidy of human gametes?
Haploid
How many total chromosomes are in a karyotype showing trisomy (three) 21?
47
How many daughter cells are produced by meiosis? (include ploidy)
four unique haploid cells
What is the phenotypic ratio results from AaBb × AaBb?
9:3:3:1 =DD:DR:RD:RR
Two unaffected parents produce an affected child → what inheritance pattern?
During which stage of the sexual life cycle does ploidy change from haploid to diploid?
Fertilization
Which meiotic phase shows homologous pairs aligned at the metaphase plate?
Metaphase I
What event happens only in meiosis I and not mitosis?
Homologous chromosome pairing (synpasis) and crossing over
In a monohybrid cross Aa × Aa, what fraction are homozygous dominant?
1/4
Which process creates genetically unique gametes?
Meiosis
In humans, which cells are diploid—somatic or gametes?
Somatic Cells
What is the key event of Anaphase I?
Homologous chromosomes separate
In which stage do sister chromatids separate in meiosis?
Anaphase II
A black mouse (Bb) × white (bb). What % of offspring are white?
50%
Why aren’t mutations in skin cells passed to offspring?
Skin cells are somatic not gametes
Draw or describe one full cycle from zygote → adult → gamete → zygote, identifying: mitosis, or meiosis, or fertilization.
Zygote (2n) → mitosis → adult (2n) → meiosis → gametes (1n) → fertilization → zygote (2n)
What visual evidence in a karyotype reveals a chromosomal disorder?
Extra or missing chromosomes
Name two ways meiosis creates genetic diversity.
Crossing over
Independent assortment
In a dihybrid cross AaBb × AaBb, what fraction shows both recessive traits?
1/16
Define an allele.
Different version of the same gene