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What are alleles? Homozygous/heterozygous?
Alleles are different forms of a gene. Homozygous means having two of the same alleles (RR).
Heterozygous means having two different alleles (Rr).
What happens to the chromosomes when a cell enters mitosis?
Spindle fibers align the chromosomes along the middle of the cell nucleus. The paired chromosomes
separate at the kinetochores and move to opposite sides of the cell. Chromatids arrive at opposite
poles of cell, and new membranes form around the daughter nuclei.
What is a karyotype? When is it useful?
A karyotype is the number and appearance of chromosomes in the nucleus of a eukaryotic cell. It 5 enables comparisons between species and allows scientists to see mutations. Karyotyping can be
used to screen for abnormal numbers of chromosomes or defective chromosomes associated with
certain congenital disorders.
What is the function of a centromere?
The centromere keeps the two sister chromatids together, and is where the chromosome attaches to
the spindle apparatus during mitosis and meiosis.
What happens when a somatic cell divides (mitosis)? How does this differ from when a
reproductive cell divides? What are the products of mitosis? Meiosis? What is the
function of mitosis? Meiosis?
Somatic cells- mitosis- involves one fission of the nucleus- homologous chromosomes don’t line
up-produces 2 identical diploid daughter cells with same genetic info as parent cell- produces all cells
other than sex cells
Reproductive cells- meiosis- involves two fissions of the nucleus (second one to separate
chromatids)- homologous chromosomes pair up on spindle (synapsis)- produces four gametes, or
sex cells (eggs or sperm), each possessing half the number of chromosomes of the original cellBe able to do a monohybrid and dihybrid cross (Punnett squares). What does a
punnett square tell us?
Punnett squares predict the genotypes of offspring.
What were Gregor Mendel’s contributions to our understanding of heredity?
Traits come in two forms (alleles code for genes)
One allele is dominant over the other
Law of segregation
Law of independent assortment
What are Mendel’s laws, and what do they tell us?
The principle of segregation states that each organism’s two alleles for each gene separate from each
other when gametes (eggs or sperm) form, so that each gamete receives one allele of each gene.
The principle of independent assortment states that the two alleles of one gene segregate ("sort")
independently of the alleles of other genes into daughter cells when gametes are formed during
In what ways was Mendel wrong in his understanding of heredity?
Linked genes- genes that are inherited together as they are located on the same chromosome
Multiple alleles (more than 2)
Codominance- everything is expressed equally (AB blood type)
Incomplete dominance- blended alleles (red flower + white flower= pink flower)
Sex-linked inheritance- some genes are located on sex chromosomes and therefore have a different
What are sex-linked genes? How is inheritance of sex-linked genes different from that
of genes on autosomal chromosomes?
Sex-linked genes are located on the sex chromosomes. Females have 2 X chromosomes, males have
an X and a Y. In g...
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