Unit 5: Heredity
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Diploid Cell
Diploid cells (2n) contain two complete sets of chromosomes, one inherited from each parent, totaling 46 in humans (23 pairs)
Haploid Cell
Haploid cells contain a single set of chromosomes (1n), which is half the number found in diploid cells. In humans, this equates to 23 chromosomes.
Product of Meiosis
4 haploid daughter cells
sex chromosomes vs autosomes
determine male/female vs determines all other factors 22 autosomes, 1 sex chromosome
Haploid
Haploid cells contain a single set of chromosomes ((n)), which is half the number found in diploid ((2n)) somatic cells. In humans, this equates to 23 chromosomes
Synapsis
synapsis is the crucial pairing of homologous chromosomes (one from each parent) during prophase I of meiosis
crossing over and recombinant chromatids
Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I of meiosis, creating genetic variation. This process swaps segments of DNA, resulting in recombinant chromatids, which are chromosomes that possess new combinations of alleles different from the parent.
What separates in Meiosis I vs Meiosis II?
Meiosis I - homologous chromosomes separate Meiosis II - sister chromatids separate
Chromosome number reduced from diploid to haploid
Meiosis I
Chromosome # of gametes
n (haploid)
2 processes that increase genetic variation
Crossing over and independent assortment
Mitosis makes 2 identical diploid cells while Meiosis makes…
4 genetically different haploid gametes from sexual reproduction
When does crossing over occur in meiosis?
Prophase 1
when does independent assortment occur?
metaphase 1
what happens in Anaphase II?
Sister chromatids separate and are pulled to opposite poles
Allele
different version of same. gene
Mendels law of Segregation
diploid organisms possess two alleles for each trait, which separate during meiosis so that each gamete receives only one allele
Heterozygous vs Homozygous vs Homologous
Homozygous and heterozygous describe allele pairs (genotypes) at a specific gene locus, while homologous describes a pair of chromosomes
Incomplete dominance
Blend of traits
Codominance
Both alleles fully expressed (Blood type. for ex.)
Dihybrid cross
examines the inheritance of two different traits simultaneously
When does independent assortment occur?
Metaphase I
Ultimate goal of meiosis
to make genetically different gametes
What happens to sister chromatids by start of Meiosis II
They are no longer identical