Exam 4: Chapters 11 And 12 Flashcards
Allele
Alternate versions of the same gene; different nucleotide sequence
Diploid
Having 2 sets of genes (two copies of each chromosome) (humans are diploid organisms)
Haploid
Having only one set of genes (one copy of each chromosome)(human gametes are haploid)
Gametes
Haploid reproductive or sex cells (sperm or egg in humans)
Zygote
First haploid cell of new generation, develops by mitosis into an embryo
Genotype
An organism’s genetic makeup (alleles you have)
Phenotype
Physical or observable features
Homozygous
Having 2 identical alleles
homo=“same”, AA or aa
Heterozygous
Having 2 different alleles of a gene (hetero=“other” Aa)
Dominant
Determines phenotype if present in 1 or 2 copies (uppercase letter)
Recessive
Affects phenotype only if 2 copies are present, masked by dominant if present in 1 copy only (lowercase letter)
Carrier
Individual who have one copy of the recessive allele but appeal normal are carriers of the disorder (heterozygotes)
Autosomal vs. sex linked traits
Sex linked: (man / woman)
(Woman: XX)
(Man: XY)
Autosomal: both men and women receive the same traits/genes
Nondisjunction
Failure of chromosomes to separate during cell division
What does it mean to say they carry equivalent genes?
?
How many genes chromosomes are in human gametes
23
Meiosis involves ________ of cell division
A special type of cell division producing genetically diverse gametes
In which phase of meiosis I or II does each of the following occur
(specify prophase I, metaphase II, anaphase III, telophase IIII)
A. Sister chromatids begin moving to opposite poles
Anaphase II
In which phase of meiosis I or II does each of the following occur
(specify prophase I, metaphase II, anaphase III, telophase IIII)
B. Recombination between homologous chromosomes
Prophase I
In which phase of meiosis I or II does each of the following occur
(specify prophase I, metaphase II, anaphase III, telophase IIII)
C. Homologous pairs begins to separate
Anaphase I
In which phase of meiosis I or II does each of the following occur
(specify prophase I, metaphase II, anaphase III, telophase IIII)
D. Cytokinesis begins, chromosomes are still doubled
Telophase I
What are two sources of genetic variation in meiosis? Explain both.
- Recombination of homologous chromosomes
- Independant assortment (random lining up between chromosomes on the equator)
Why and with what genotypes would you perform a testcross
- you do it when you have a dominant genotype cross it with a recessive genotype
- an individual of dominant phenotype (but unknown genotype)
- a homozygous recessive individual
Why are genetic disorders NOT eliminated by natural selection? What is heterozygote advantage (give an example)
- heterozygous has a different genotype
- last onsetive disease
- medical advances
How is gender determined in humans
Be the male (sperm)
Does recombination occur between the X and Y chromosome? Why or why not
No because he Y is too short (not homologous) and it doesnt have enough information
(When maternal and paternal chromosomes pair and physically exchange DNA segments)
- the X chromosome
(Woman: XX)
( Man: XY)
Know the difference between complete dominance and incomplete dominance or co-dominance.
Ex: Red and White flower mix=
• complete dominance= dominant phenotype and recessive phenotype
• Incomplete dominance= when red and white mix, it equals the pink flower
• Codominance= red and white flower and blood type
How do phenotypes and heterozygotes differ? Give an example of incomplete dominance and an example of codominance
ADD ANSWER TO FIRST QUESTION
Ex: Red and White flower mix=
- Incomplete dominance= when red and white mix, it equals the pink flower
- Codominance= red and white flower
What is polygenic inheritance? Give 2 examples
A single trait determined by the interaction between alleles of more than one gene (more than one gene pair contributes to a single gene type)
Ex: human height (shows continuous variation)
: skin color
* continuous generation
Give an example of a disorder caused by nondisjunction
Aneuploidy: an abnormal number of one or more chromosomes
Trisomy 21/Down Syndrome : risks of both increase maternal age
When can nondisjunction happen
During meiosis produces aneuploid sperm and egg cells with too few or too many chromosomes
- Anaphase I
- Anaphase II
