Biology Unit
A punnett square is a two by two square which is used to predict the possible phenotypes of offspring, and its ratio. (Krough)
b) The male and female gametes contain only one set of alleles. (Krough)
c) The genes of the parents go on the outside of the boxes. (Krough)
d) The possible gene outcome from the parental genes goes inside the boxes. (Krough)
e) The punnett square always contains only 4 boxes or squares, that is, two rows and two columns. (Krough)
a) The Law of segregation is based on Mendel's pea plant experiment where he came to the conclusion that alleles for a trait separate when gametes are formed and are randomly paired at fertilization, after which one allele is expressed dominantly while the other is masked. (Krough)
b) Law of independent assortment states that alleles separate independently during gamete formation, which means that traits are inherited by offspring independently of each other.
c) It allows us to predict the progeny phenotypes. (Krough)
3. a) Test cross is an experimental cross of an individual organism with dominant phenotype (but unknown genotype) with an organism with a known homozygous recessive phenotype and genotype. (Krough)
b) A test cross is used to determine an organisms genotype. (Krough)
c) An organism with a dominant phenotype (but unknown genotype) is crossed with an organism with a known homozygous recessive phenotype and genotype. (Krough)
d) If only fifty percent of the offspring are reflecting one phenotype, whereas the other fifty percent is reflecting the other phenotype, the unknown genotype is a heterozygous dominant, for example, Bb. If all the progeny are reflecting only the dominant phenotype, then the unknown genotype is a homozygous dominant, for example, BB. (Krough)
4. a) The purpose of pre-natal diagnostic testing is to monitor fetal growth and development, lung maturity and to check chromosomal abnormalities in order to enable early medical intervention and prenatal counseling. (Krough)
b) This technique sends high frequency sound waves which are reflected to different degrees by body organs. These waves are measured and displayed on a screen. (Krough)
c) In amniocentesis, a thin needle is passed through the abdomen and a sample of amniotic fluid is collected. (Krough)
d) After administering local anesthesia, chorionic villus sampling is performed by passing a catheter through the cervix or a needle through the abdomen to collect a sample of the placenta. (Krough)
5.a) If organisms were made independently, their distribution across the globe would also be independent. Biogeography tells us that genetically similar species are not distributed evenly, hence proving the evolutionary theory. (Krough)
b) The occurrence of homologous structures within different species provides strong evidence that individual species were formed as a result of divergence from a common ancestor. (Krough)
c) The biochemistry of different species is closely related, providing evidence of decent from a common ancestor. (Krough)
6.a) Natural selection is the process by which only organisms fit to survive in a particular environment survive long enough to pass their traits to their offspring, thus increasing in number. (Krough)
b) Organisms best adapted to survive, in a particular environment, are preferentially selected by the environment they live in. (Krough)
c) The sickle cell trait in Africa has a protective role against malaria. People heterozygous for the disease are preferentially selected since it protects them against malaria with minimal effects of the disease itself. People homozygous for the disease are protected from malaria but they do not survive long enough due to the effects of the disease. People without the gene, are exposed to the fatal effects of malaria in the region. (Krough)
7.a) Genetic drift, gene flow, mutation, non-random mating and natural selection (Krough)
b) Genetic drift: genetic drift affects a population's gene pool but unlike natural selection, it does not help in adaptation. (Krough)
Gene flow: it may cause a difference in the allelic frequency of a particular trait. It can also add new alleles to the gene pool. (Krough)
Mutation: mutations can be either beneficial or harmful. Beneficial mutations can be naturally selected, thus adding to the gene pool. (Krough)
Non-random mating: non-random mating minimizes the chance of gene diversification. (Krough)
Natural selection: this phenomenon allows the transfer of useful alleles, necessary for survival, to their progeny. (Krough)
8.) Gene mutations cause a change in the codon sequence, which may prematurely inhibit any further addition of amino acids or may code for a different amino acid. This changes the end product forming a completely new protein, hence producing gene variation.
The cross over process in sexual recombination also allows formation of gene combinations in the offspring, hence increasing genetic variation. (Krough)
9.) Pre-zygotic and post-zygotic barriers are the two kinds of reproductive barriers. Reproductive barriers prevent species from producing fertile or viable offspring, which prevents speciation. (Krough)
10.a) A localized group of individuals that belong to the same species are called population. (Krough)
b) Species are a group of populations that can interbreed and produce viable offspring. (Krough)
c) A population is the smallest unit that can evolve. (Krough)
11.) On land, organisms must be able to conserve water, exchange gasses, have a
Genetics Student Response Original DNA Strand: 3'-T ACCCTTTAGCCACT-5' Transcription (base sequence of RNA): 3'-A UGGGAAAUCGGUGA-5' Translation (amino acid sequence): Met -- Gly -- Asn -- His -- Arg -- STOP Mutated gene sequence one: 3'-T ACGCTTTAGCCATT-5' Transcription (base sequence of RNA): 3'-A UGCGAAAUCGGUAA-5' Translation (amino acid sequence): Met -- Arg -- Asn -- His -- Arg -- STOP Mutated gene sequence two: 3'-T AACCTTTACTAGGCACT-5' Transcription (base sequence of RNA): 3'-A UUGGAAAUGAUCCGUGA-5' Translation (amino acid sequence): Ile -- Gly -- Asn -- Asp -- Pro-STOP What is the significance of the
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