Genetics Test Study Guide
Biology 10Genetics Test Study Guide
Remember to review all of your vocabulary, notes, and textbook information!
1. Basic terms and conceptsa) Genes and chromosomesb) Dominant allele/trait vs. recessive allele/traitc) Genotype vs. phenotyped) Homozygous vs. heterozygouse) One-factor or monohybrid cross (1-gene = 1-characteristic = 1 type of letter)f) How did Mendels work differ from other scientists investigating heredity? particulate inheritance (instead of blending of traits) used mathematics/statistics in data analysis
2. Law of Segregation as applied in monohybrid crossesState the law: _____________________________________________Solve all the cases given below using Punnett squares. Predict offspring genotypes and phenotypes and give the genotypic/phenotypic ratios.a) Case 1: Complete Dominance (Mendelian genetics) RR (homozygous red) x rr (white)Ex:
RrRr R R r100% Rr
RrRr 100% red r G.R. = 4 Rr : 0 P.R = 4 red : 0 RR (homozygous red) x Rr (heterozygous red)
Rr (heterozygous red) x rr (white)
Rr (heterozygous red) x Rr (heterozygous red)
b) Case 3: Incomplete dominance (Explain: _____________________________)
CRCR (red snapdragon) x CWCW (white snapdragon)
CRCR (red snapdragon) x CRCW (red+white=pink snapdragon)
CRCW (pink snapdragon) x CWCW (white snapdragon)
CRCW (pink snapdragon) x CRCW (pink snapdragon)
Why is it possible for offspring to have traits that cannot be found in parents?
c) Case 4: Multiple Alleles (Explain:____________________________) and Codominance (ABO blood group)Which of the following couples will produce the most variety of offspring phenotypes? IAIA x IAIB IAi x IAIB IAIB x IAIB IAIB x IBi IAIB x ii IAi x IBi
Using Punnett Squares, show the outcomes/offspring/progeny of the ALL of the above genetic crosses in ALL cases!!!
d) Case 5: Polygenic Traits (Explain:___________________________) A polygenic trait is determined by many genes located in various loci that may be located in different chromosomes Example genotype: AAbbCcDd gives rise to one trait common examples are human __________ and ________ (black is dominant over white; and tall is dominant over short} the more dominant alleles you inherit from both parents that darker your skin is (e.g. AABBCC) and vice versa polygenic traits can be described in more or less terms, not as either-or
e) Case 6: Sex-linked Traits (Explain:__________________________) are traits that are associated with sex (mostly males!) and are determined by genes (mostly recessive allele!) located on the X chromosome (Y-linked conditions are rare!) Why do sex-linked traits occur more often in males than in females?
in humans: colorblindness, hemophilia (=h) (H = normal allele) in fruit flies: white eye color (=r) (R = red eye allele) name the phenotypes of each of the following genotypes:XHXHXHXhXhXhXHYXhY which one is the carrier? ________ (remember: a carrier is unaffected!!) use Punnett Square to solve problems: e.g. What is the probability that a carrier mother and a normal father will have a hemophiliac child?
Criss-cross inheritance: mother passes on allele to son; father passes it on to daughter
f) Case 7: Sex Determination How is sex inherited in humans? Draw a punnett square below:
Differentiate autosomes vs. sex chromosomes: _________________________________________________________________ Remember: all cells contain autosomes + at least one sex chromosome 1 set of 23 (haploid set) comes from the mother = maternal chromosomes; and the other haploid set comes from the father = paternal chromosomes Y determines gender male (no Y means female) XX = female; XY = male What is the gender of a person with XXY? _______
3. Law of Independent Assortment
State the law: _____________________________________________
Is independent assortment the only source of genetic variation? How about linked genes in parents? Can these genes get unlinked and therefore recombine to produce mixed traits in offspring?
4. Chromosomal Theory of HeredityState the theory: __________________________________________________________________________________________________Draw a pair of homologous chromosomes with 4 loci for 4 genes; 1 locus is homozygous dominant, 1 homozygous recessive, 1 heterozygous (incompletely dominant), 1 heterozygous (codominant)
5. Mutations and Genetic Disorders Chromosomal mutations involve change in chromosomes: change in chromosome structure due to alterations in fragments or parts of a chromosome (describe: deletion, inversion, duplication, translocation) change in chromosome number due to nondisjunction of a pair of homologous chromosomes leads abnormal chromosome number change in chromosome set due to nondisjunction of the whole set of chromosomes leads to multiple sets of chromosomes (polyploidy)Karyotyping detects genetic disorders that involve abnormal number of chromosomes (either 1 extra or one missing) you must be able to identify: Down, Klinefelter, Turner, and Triple X syndromes
Point mutations involve change in a single nucleotide: base substitution may have no effect or may change the amino acid sequence and protein structure, thus altering its function, thus altering the trait base deletion/addition causes frameshift mutation, thus changing the entire protein, thus definitely changing the trait
Do mutations contribute to genetic variation? YES! By creating new alleles. [You see, sex though meiosis only reshuffles existing alleles. Mutation, on the other hand, produces new alleles.]
Name a genetic disorder whose cause can be explained by any of the chromosomal mutation OR point mutation mechanisms above. Discuss the cause (mutation change in protein structure and function change in cell function change in trait of organism), symptoms, and treatment.
6. Meiosis a) What is the purpose of meiosis? (relate meiosis to sexual reproduction)
b) How do gametes differ from somatic cells?
c) How does meiosis differ from mitosis?
d) How does meiosis change a diploid cell into haploid cells?
e) In what phase does crossing over take place?
f) In what phase of meiosis does Mendels Law of Independent Assortment happen?
g) How does meiosis contribute to genetic variation? (discuss 2 mechanisms) How does sexual reproduction contribute to genetic variation? (this question incorporates the previous one just add one more mechanism that has something to do with fertilization)
How are genetics and evolution (by natural selection) linked?