Chapter 25
What is complementary base pairing?
Nitrogenous bases are bonded in specific pairs
A-T and C-G
What is apoptosis?
What is its purpose?
programmed cell death
prevents unwanted or mutated cells
When two or more genes with multiple alleles affect the same trait in an additive fashion, it is termed
polygenic inheritance
What genotype results in Klinefelter Syndrome? Turner Syndrome?
Klinefelter: XXY
Turner: X
define vestigial structure
provide an example
Anatomical features that are fully developed and functional in one group of organisms but reduced and functionless in a similar group are termed
tailbone or appendix in humans, pelvic bones in whales
Why is DNA replication considered semiconservative?
Each new strand of DNA is made from a new strand and an old strand from the original DNA
Define cytokinesis
When does this occur?
division of the cytoplasm
following telophase
Define genotype and phenotype
genotype: genetic information, alleles present (ex. Bb)
phenotype: physical appearance, expression of the genes (ex. brown eyes)
How is hemophilia inherited?
absence of the clotting factor
X-linked recessive disorder (similar to color-blindness)
Movement of alleles between populations, such as by the migration of breeding individuals is called
gene flow
What is the purpose of mRNA?
carry genetic information from DNA out of the nucleus and to the ribosome (rRNA)
Describe three differences between meiosis and mitosis
Meiosis: 4 daughter cells, genetically different, two divisions, crossing over, gametes, etc.
Mitosis: 2 daughter cells, genetically identical, one division, somatic cells, etc.
Define incomplete dominance and codominance
provide an example
Incomplete dominance: a heterozygote expresses a blend of the two phenotypes, pink flower from red and white parents
Codominance: a heterozygote expresses both phenotypes equally, an AB blood type from A and B type parents
Define nondisjunction
failure of chromosomes to separate properly during cell division, daughter cells have wrong number
What is a species isolating mechanism?
What are two types of isolating mechanisms?
properties of two species that prevent them from interbreeding
habitat, temporal, behavioral, mechanical, gametical, etc.
What are the two steps that occur for gene expression?
Generally, what happens in each step?
2. Translation (RNA -> protein)
What are homologous chromosomes?
chromosomes that carry the same genetic information but are not identical
one from each parent
Tail length is a dominant trait in cats. What are the expected genotypic and phenotypic ratios for the offspring if a heterozygous parent is crossed with a homozygous recessive parent?
50% heterozygous, 50% homozygous recessive
50% long-tailed, 50% short-tailed
What does it mean to say genes are "linked?"
alleles are close together, do not display independent assortment
Consider the phylogenetic tree. Which of the following species are most closely
related?
A. chimpanzee and rhesus monkey
B. gibbon and capuchin
C. rhesus monkey and capuchin
D. galago and green monkey
chimpanzee and rhesus monkey
initiation: rRNA, mRNA, and tRNA are brought together
elongation: amino acids are brought to ribosome by tRNA using codons on mRNA, polypeptide is built
termination: rRNA subunits separate, fully formed protein is released
What are the four phases of mitosis?
What occurs at each step?
prophase: chromosomes condense, spindle fiber appears, nuclear envelope disappears
metaphase: chromosomes line up at the metaphase plate
anaphase: sister chromatids are pulled to opposite poles of the cell
telophase: nuclear envelope reforms, chromosomes become uncondensed, spindle fiber disappear
In humans, aniridia, a type of blindness, is due to a dominant allele A. Migraine headaches are due to another dominant allele M. If a man who suffers from both conditions (AaMm) marries a woman who suffers from both (AaMm), what are the chances of an offspring expressing both traits.
9/16
If a woman is a carrier for the color-blind recessive allele and her husband has normal vision, what are their chances that a son will be color-blind?
50%
1. No mutations
2. No gene flow
3. No genetic drift
4. Nonrandom mating
5. No natural selection