gen bio 1406 exam 4

What are linked genes

Genes on the same chromosome that tend to be inherited together.

What are sex-linked genes

Genes located on one of the sex chromosomes.

How many recessive alleles must females have to express an X-linked recessive trait?

Two.

How many recessive alleles must males have to express an X-linked recessive trait?

One.

What are parental types?

Offspring with phenotypes matching the parents.

What are recombinant types?

Offspring with new (non-parental) phenotypes.

What mechanism produces recombination?

Crossing over between homologous chromosomes in meiosis.

The closer two genes are, the _______ the recombination frequency.

Lower.

The closer two genes are, the _______ likely crossing over will occur.

Less.

What is nondisjunction?

Failure of homologous chromosomes to separate properly in meiosis.

What is aneuploidy?

Abnormal number of chromosomes due to nondisjunction.

How many copies of a chromosome are in a monosomic zygote?

One.

How many copies of a chromosome are in a trisomic zygote?

Three.

What causes Down syndrome?

Trisomy 21.

Polyploidy = more than ___ sets of chromosomes.

Two.

Triploidy = ___n

3n.

Tetraploidy = ___n

4n.

Define deletion.

Loss of a chromosome segment.

Define duplication.

Repetition of a chromosome segment.

Define inversion.

A chromosome segment is reversed.

Define translocation.

A fragment moves to another chromosome.

Before replication: how many DNA molecules per chromosome?

One.

After replication: how many DNA molecules per chromosome?

Two sister chromatids held by cohesins.

Griffith's experiment showed...?

Harmless bacteria become pathogenic when mixed with heat-killed pathogenic bacteria.

Avery, McCarty, McLeod discovered...?

DNA is the transforming substance.

Chargaff's rules?

A=T and C=G within a species; DNA composition varies between species.

Hershey & Chase proved...?

DNA is the genetic material of viruses.

DNA replication model?

Semiconservative.

Each strand serves as a _________ for new strand synthesis.

Template.

Three components required for replication?

Parental DNA, enzymes, nucleotides.

Replication begins at...?

Origins of replication.

Prokaryotes have how many origins?

One.

Eukaryotes have how many origins?

Many.

Replication occurs in what direction?

5' → 3'.

What is found at ends of replication bubbles?

Replication forks.

Helicase function?

Unwinds DNA.

Single-strand binding proteins function?

Stabilize unwound DNA.

Topoisomerase function?

Relieves tension ahead of fork.

Primase function?

Synthesizes RNA primers.

DNA polymerase III function?

Adds nucleotides to primer.

DNA polymerase I function?

Replaces RNA primers with DNA.

Ligase function?

Joins DNA fragments.

Leading strand is synthesized...?

Continuously.

Lagging strand is synthesized...?

Discontinuously in Okazaki fragments.

What is a replisome?

All enzymes working together during replication.

What are telomeres?

Protective repeated DNA sequences at chromosome ends.

Telomerase function?

Extends telomeres using an RNA template.

What is gene expression?

The process by which DNA directs protein synthesis.

What are the two steps of gene expression?

Transcription and Translation.

Central Dogma pathway?

DNA → RNA → Protein.

Transcription: DNA → ?

RNA.

All RNA is made from a _______ template by ________.

DNA; RNA polymerase.

Types of RNA?

mRNA, rRNA, tRNA.

Codons are read in what direction?

5' → 3'.

Total number of codons?

64.

Number coding for amino acids?

61.

Stop codons?

UAA, UAG, UGA.

Start codon?

AUG.

What is a degenerate code?

Multiple codons specify the same amino acid.

Required enzyme for prokaryotic transcription?

RNA polymerase.

Promoter, start site, termination site = ?

Transcription unit.

Three transcription steps?

Initiation → Elongation → Termination.

What helps RNA polymerase find promoter?

Transcription factors.

mRNA modifications?

5' cap, poly-A tail, splicing.

Translation: RNA → ______?

Protein (polypeptide).

tRNA has two key parts?

Attached amino acid + anticodon.

Ribosome subunits?

Large + small; made of rRNA + proteins.

Ribosome functions?

Decodes mRNA; forms peptide bonds.

Enzyme forming peptide bonds?

Peptidyl transferase.

1st step of translation?

Initiation.

2nd step?

Elongation.

3rd step?

Termination.

Silent mutation?

Changes nucleotide, same amino acid.

Missense mutation?

Changes amino acid.

Nonsense mutation?

Changes codon to STOP.

Frameshift mutation?

Reading frame shift due to insertion or deletion.

Mutations are the source of ______?

Evolutionary variation.

What is the blending inheritance hypothesis?

The idea that parental traits blend together in offspring.

What organism did Mendel use in his experiments, and why?

Pea plants — they can hybridize, cross-fertilize, and self-fertilize.

A monohybrid cross examines how many traits?

One trait.

What is the P generation?

The parental generation of two true-breeding strains.

In the F1 generation, all offspring resembled which parent?

The dominant parent.

The alternative to a dominant trait is a _______ trait.

Recessive.

In the F2 generation, recessive traits reappear after what process?

Self-fertilization of F1 plants.

What is a true-breeding organism?

One whose offspring always look like the parents (homozygous).

What is genotype?

The set of alleles an organism has.

What is phenotype?

The physical expression of the genotype.

What does the P allele correspond to?

Dominant allele, purple color.

What phenotype does genotype pp result in?

Homozygous recessive → white flowers.

What is the F1 generation genotype ratio?

All Pp.

What is the F2 genotype ratio?

1 PP : 2 Pp : 1 pp.

What is the F2 phenotype ratio?

3 purple : 1 white.

How many traits does a dihybrid cross examine?

Two.

What does allele R represent?

Dominant allele → round peas.

What does allele Y represent?

Dominant allele → yellow peas.

What is the F2 phenotype ratio in a dihybrid cross?

9:3:3:1 (9 round yellow, 3 round green, 3 wrinkled yellow, 1 wrinkled green).

What is a testcross used for?

To determine whether an individual with a dominant phenotype is homozygous or heterozygous.

How do you set up a testcross?

Cross the unknown with a homozygous recessive.

What is a Mendelian inherited trait?

A trait controlled by one gene with clear dominant/recessive alleles.

What are examples of Mendelian traits?

Widow's peak, cleft chin, earlobe shape, albinism, achondroplasia, cystic fibrosis.