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In a dihybrid cross of heterozygotes, what proportion of the offspring will be phenotypically dominant for both traits?
Consider pea plants with the genotypes GgTt and ggtt . These plants can each produce how many type(s) of gametes?
four ... one
Two organisms with genotype AaBbCcDdEE mate. These loci are all independent. What fraction of the offspring will have the same genotype as the parents?
You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits?
Red shows incomplete dominance over white.
Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height?
- a combination of polygenic inheritance and environmental factors
- Several genes (polygenic inheritance) control height in humans, giving an overall normal distribution. Environmental factors such as nutrition smooth out the curve.
What can we observe in order to visualize Mendel's Law of Segregation?
homologous chromosomes separating during meiosis I
A white-eyed female Drosophila is crossed with a red-eyed male Drosophila. Which statement below correctly describes the results?
- None of the females will have white eyes.
- All of the females will have red eyes because they will inherit the dominant red-eye allele from their male parent.
In general, the frequency with which crossing over occurs between two linked genes depends on what?
how far apart they are on the chromosome
Which of the following results in a situation in which the chromosome number is either 2n+1 or 2n-1 ?
- An aneuploid individual has either too many or too few chromosomes, usually as a result of nondisjunction.
What results if a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction?
What phenomenon occurs when a particular allele will either be expressed or silenced, depending on whether it is inherited from a male or a female?
- genomic imprinting
- The sex of the parent transmitting a given chromosome can affect the chromosome's expression in the offspring.
How are human mitochondria inherited?
- from the mother only
- An individual's mitochondria are all derived from those found in the ovum.
What is true of an X-linked gene, but not of a Y-linked gene?
The gene is present in both males and females.
Griffith's experiments with S. pneumoniae were significant because they showed that traits could be transferred from one organism to another. What else did he find that was significant?
- The transferred traits were heritable.
- The fact that offspring of transformed bacteria also showed the pathogenic trait meant that the transforming agent had to be involved with the genetic material.
In the Hershey and Chase experiment that helped confirm that DNA, not protein, was the hereditary material, what was the key finding?
- Radioactively labeled phosphorus was present inside the infected bacteria.
- When the bacteria had been infected with T2 phage whose DNA was tagged with radioactive phosphorus, the pellet of mainly bacterial material contained most of the radioactivity, indicating that the labeled phage DNA had entered the cells.
Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA?
DNA replication is said to be semiconservative. What does this mean?
- Each new double helix consists of one old and one new strand.
What is the function of helicase in DNA replication?
It untwists the double helix and separates the two DNA strands.
In nucleotide excision repair, damaged DNA is excised by what enzyme(s)?
endonuclease - enzymes that cut DNA
What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?
telomeres, consist of many copies of a short DNA sequence that is bound by specific proteins
What is true of DNA during interphase?
It exists as chromatin and is less condensed than mitotic chromosomes.
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.
- three, amino acids
- Three nucleotide bases make up a codon and specify which amino acid comes next in the sequence.
Where does RNA polymerase begin transcribing a gene into mRNA?
- after a certain nucleotide sequence called a promoter
- In both eukaryotes and prokaryotes, RNA polymerase binds to the gene's promoter and begins transcription at a nucleotide known as the start point, although in eukaryotes the binding of RNA polymerase to the promoter requires transcription factors.
What is the function of RNA polymerase?
- it unwinds the double helix and adds nucleotides to a growing strand of RNA
- RNA polymerase has several functions in transcription, including unwinding the DNA double helix and adding RNA nucleotides
After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence?
- introns ... exons
- Introns, intervening sequences, are removed and the exons, expressed sequences, are spliced together.
What is a ribozyme?
- a biological catalyst made of RNA
- A number of examples of biological catalysts containing RNA have been discovered, including ribozymes, snRNAs, and ribosomes themselves.
What is true of tRNAs?
- Each tRNA binds a particular amino acid.
- Aminoacyl-tRNA synthetase joins a specific amino acid to a tRNA, a single strand of RNA about 80 nucleotides long.
How is translation initiated?
- The small ribosomal subunit binds to the mRNA.
- The tRNA bearing methionine binds to the start codon.
- The large ribosomal subunit binds to the small one.
- The start codon signals the start of translation.
What does a mutagen cause?
- a change in the sequence of DNA
- Mutations are changes in the genetic material of the cell.
What is a gene?
- A gene codes for either a polypeptide or an RNA molecule.
- One gene may code for several polypeptides. We have also discovered many RNA molecules with diverse but important functions in the cell.
Why is UV radiation damaging to cells?
- it causes mutations in DNA
- it is an example of a physical mutagen
What technique did Watson and Crick use to develop their model for the structure of DNA?
- x-ray crystallography
- they stole it from Rosalind Fraklin, duh
Major difference between bacterial and eukaryotic chromosomes?
bacterial chromosomes are circular, eukaryotic chromosomes are circular
What will happen if an incorrect base is added into the DNA during replication?
It can be repaired by the mismatch repair system
What does DNA polymerase I do?
It removes the RNA primer and adds DNA nucleotides in the 3' end of the Okazaki fragments in its place.
What does topoisomerase do?
- cuts the DNA
- allows it to spin around its central axis, which relieves the strain caused by twisting
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