Exam 2 Flashcards
What are the three component parts of a nucleotide?
Sugar, phosphate, and a base.
Which parts make up the structural ‘sides of a ladder’ part of a DNA molecule?
Sugar and phosphate.
What is the relationship among DNA, a gene, and a chromosome?
A chromosome contains hundreds of genes which are composed of DNA.
Name one difference between DNA and RNA.
DNA contains thymine, and RNA contains uracil. DNA contains deoxyribose sugar, and RNA contains ribose sugar. DNA is usually double-stranded, and RNA is usually single-stranded.
Define mutation.
A change in the DNA sequence.
Why are mutations important?
They provide variation that can result in evolutionary change.
How can a gene be mutated with no resulting change in the protein that is produced from that gene?
A codon has changed, but it codes for the same amino acid as the original codon.
What is a Barr body?
An inactivated X chromosome in female mammals.
Define genotype.
The combination of alleles carried by an individual.
Define phenotype.
The physical expression of the genotype.
Define heterozygote.
An individual whose two alleles for a gene are different forms.
Define incomplete dominance.
Heterozygotes show an intermediate phenotype.
Define genetic codominance.
The phenotype of the heterozygote expresses the traits of both alleles present.
What is the result of nondisjunction during meiosis?
Abnormal chromosome numbers.
What are the possible genotypes for an individual who is square and has green toes, given R = round, r = square, G = green toes, and g = pink toes?
rrGG or rrGg
During which specific stage of the cell cycle are the chromosomes replicated?
S phase of interphase.
In what phase of meiosis does synapsis of homologous pairs occur; crossing over may occur?
Prophase I.
In what phase of meiosis are individual chromosomes aligned at the center of the cell?
Metaphase II.
In what phase of meiosis do homologous chromosome pairs separate and move away from the middle of the cell?
Anaphase I.
A cell with a diploid (2N) chromosome number of 18 undergoes mitosis. How many daughter cells will be produced and how many chromosomes will each daughter cell contain?
2 daughter cells, each with 18 chromosomes.
A cell with a diploid (2N) chromosome number of 18 undergoes meiosis. How many daughter cells will be produced, and how many chromosomes will each daughter cell contain?
4 daughter cells, each with 9 chromosomes.
What are the names of the steps of protein synthesis?
Transcription and Translation.
Where does transcription take place?
Nucleus.
Where does translation take place?
Ribosomes in the cytoplasm.
What is the role of mRNA?
Carries information from DNA to the ribosomes.
What is the role of tRNA?
Brings amino acids to the ribosomes.
What is a codon?
An mRNA triplet that codes for a specific amino acid.
What is an anticodon?
A set of 3 nucleotides on tRNA that matches codons.
What bases are complementary to each other in DNA?
A=T and C=G.
What is the product of translation?
A protein.
What is the definition of a gene?
An actual piece/segment of a DNA molecule in the cell’s nucleus. Most genes carry information for the synthesis of a single protein.
What is the flow of information in gene expression?
DNA -> RNA -> Protein.
What is the role of RNA polymerase in transcription?
RNA polymerase finds the promoter, unwinds DNA, and links nucleotides to synthesize a single strand of mRNA using bases complementary to those in the DNA.
What is the start codon?
The start codon initiates translation.
What occurs during the elongation cycle of translation?
tRNAs deliver amino acids to the ribosome to be attached together.
What happens when tRNA reaches a stop codon?
Translation terminates and the pieces disassemble.
What is the possible effect of a mutation in a somatic cell?
It can change the protein and thus the phenotype, have no effect (silent mutation).
Name three types of mutations.
Insertion, deletion, and translocation mutation.
What is the effect of insertion or deletion mutations?
They can change the entire sequence.
What is the role of mutations in evolution?
Mutations provide the raw material for evolution.
What are homeotic genes?
‘Master genes’.
What is the SRY gene?
A ‘master gene’ on the human Y chromosome that controls expression of testis formation.
What are proto-oncogenes and tumor suppressor genes?
Genes in which mutations can cause the cell cycle to occur repeatedly and rapidly, potentially leading to cancer.
What key feature distinguishes meiosis from mitosis?
Pairing/crossing over of homologous chromosomes.
What is the result of meiosis?
Haploid cells with recombinant chromosomes.
State Mendel’s Law of Segregation.
Allele pairs separate or segregate during gamete formation and randomly unite at fertilization.
State Mendel’s Law of Independent Assortment.
Allele pairs separate independently during the formation of gametes; therefore, different traits are transmitted to offspring independently of one another.
What are linked genes?
Genes on the same chromosome that tend to be inherited together.
How is sex determined in humans?
Sex chromosome carried by sperm determines sex.
Why will sex-linked traits be expressed in males more often than in females?
Males carry only one copy of genes on the X chromosome.
What is incomplete dominance?
Heterozygotes show an intermediate phenotype.
Give an example of multiple alleles.
Human A, B, O blood types.
What is pleiotropy?
Single genes affect more than one phenotypic trait.
What are carriers in the context of single-gene disorders?
Heterozygotes for a recessive condition.
How does DNA replication ensure genetic constancy during cell division?
DNA replication is semiconservative.
What are the three types of RNA and what are their functions?
Messenger RNA (mRNA) codes for building a protein, ribosomal RNA (rRNA) is part of ribosomes, and transfer RNA (tRNA) brings amino acids to the ribosomes.
What is the definition of nondisjunction?
The failure of chromosomes to segregate/separate properly during meiosis.
