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160 Cards in this Set

  • Front
  • Back
When two or more genes reside on the same chromosome, they are said to be _____.
When two or more genes reside on the same chromosome, they are said to be linked.
Genes on the same chromosome tend to stay together during the formation of _______.
Genes on the same chromosome tend to stay together during formation of gametes.
Do linked genes always stay together? Why or why not?
No, linked genes do not always stay together homologous nonsister chromatids may exchange segments of varying lengths with one another during meiotic prophase.
What causes independent assortment of genes?
Independent assortment is due to the genes being on different chromosomes.
As genetic distance increases, the recombination frequency does what?
As genetic distance increases, the recombination frequency first increases in a linear fashion then later levels off
The map distance between two loci is given by what formula?
(Number of recombinants observed/total offspring scored ) X 100
What does a genetic map contain?
A genetic map contains the distances between the gene loci measured in terms of the frequency of recombination.
The chances of genes crossing over increases with:
The chances of genes crossing over increases with increasing distance.
The fruit fly, or the Drosophila, is an example of an organism in which the sex is depended on what?
Fruit fly, Drosophilia, sex is determined by the number of copies of X chromosomes.
Similar to humans, females have two X chromosomes and males have one X and one Y.
However, human gender is based on the presence of a Y chromosome as opposed to fruit flies where the sex is determined by the number of X chromosomes.
What are autosomes?
Any chromosome that is not a sex chromosome.
What occurs if chromosomes fail to separate during meiosis?
Nondisjunction will occur resulting in an abnormal diploid number.
What are monosomics?
Monosomics are people who have lost at least one copy of an autosome.
A trisomy is most common when which chromosome has three copies instead of two? What disease is this?
Chromosome 21 is the most common for a trisomy, this is referred to as Down syndrome.
What is the most common fatal genetic disorder of Caucasians?
Cystic fibrosis is the most common fatal genetic disorder of Caucasians.
During sickle cell anemia, how does the defective hemoglobin compare to a normal hemoglobin?
During sickle cell anemia, the defective hemoglobin differs from the normal hemoglobin by a single amino acid substitution.
Is hemophilia an example of a sex-linked condition? Is it recessive or dominant?
Yes, because the allele for hemophilia resides on the X chromosome. It is recessive.
What is an example of a hereditary disease that is caused by a dominant allele but does not express phenotypically until affected individuals are in middle age?
Huntington's Disease
What is used to diagnose genetic disorders in fetuses?
Amniocentesis
Humans have how many chromosomes?
46 chromosomes, 23 pairs.
Which is smaller; the X or Y chromosome? Why?
The Y chromosome is much smaller because few genes on this chromosome are expressed.
What is the default gender for humans?
Female
What is hemophilia?
A disease that affects a single protein in a cascade of proteins involved in the formation of blood clots.
Hemophilia is caused by what type of allele? What does that mean about men and women who have this allele on an X chromosome?
Hemophilia is caused by an X-linked recessive allele.
Women who are heterozygous for the allele are asymptomatic carriers and men who receive an X chromosome with the recessive allele exhibit the disease.
What is the term that refers to the natural process of ensuring an equal level of expression from the sex chromosomes?
Dosage compensation
In humans, the offspring gender is determined by what?
By the presence of the Y chromosome because females are the default.
The SRY gene codes for what?
SRY gene codes for androgen testosterone.
In each female cell, one X chromosome is condensed into a ____.
Barr body
What is one of the main reasons genes assort independently of one another?
They are on different chromosomes.
Linkage refers to two meanings:
1. Two or more genes can be located on the same chromosome

2. Genes that are close together tend to be transmitted as a unit
The number of linkage groups is the number of types of ___.

Example for humans?
The number of linkage groups is the number of types of chromosomes of the species.

Humans have 22 autosomal linkage groups.
Chromosomal theory of inheritance was developed by whom?
Chromosomal theory of inheritance developed in 1902 by Walter Sutton.
Chromosomal theory of inheritance:
proposed what?
based on what?
any supporting experiments?
Chromosomal theory of inheritance proposed that genes are found on chromosomes.
This was based on observations that homologous chromosomes pair with each other during meiosis.
Supporting experiments: fruit fly eye colors.
Without release of testosterone by the SRY gene and correct reception of hormone during development, an XY individual would be born with what type of phenotype?
With an XX phenotype.
What is the process in which one can determine whether an individual that displays a dominant phenotype is either heterozygous or homozygous for the trait thereby generating genotype information from phenotype information?
Testcross
Dosage compensation is only in humans. True or False?
False, all mammals exhibit dosage compensation.
What does the term genetic mosaics refer to?
What is an example?
How individual female cells may express different alleles, depending on which chromosome is inactivated.
Example: calico cat
Mitochondria DNA comes from whom and is inherited by whom?
Mitochondria DNA comes from the mother only and is inherited by both male and female offspring.
What is the primary difficulty with telomeres?
The primary difficulty with telomeres is the replication of the lagging strand.
What is aneuploidy?
The loss or gain of a chromosome, occurring in 5% of all human conceptions.
When X chromosomes fail to separate during meiosis, some of the gametes produced posses both X chromosomes, and are XX gametes. The other gametes have no sex chromosome and are designated what letter?
If there is no sex on the gamete, it is designated the letter "O".
If an XX gamete, (as a result of X chromosome nondisjunction), combines with a normal X gamete, the resulting XXX zygote develops how?
The individual will be a female with one functional X chromosome and two Barr bodies.
If an XX gamete, (as a result of X chromosome nondisjunction), combines with a normal Y gamete, the resulting XXY zygote develops how?
Klinefelter syndrome: The individual will be a male with many female body characteristics and may have diminished mental capacity.

http://images.lifescript.com/images/ebsco/images/si55551770.jpg
If an O gamete fuses with a Y gamete, what will happen to the OY zygote?
It will fail to develop further as humans cannot survive without genes on an X chromosome.
If an O gamete fuses with an X gamete, what will happen to the XO zygote?
Turner syndrome: She will become a short sterile female with a webbed neck and sex organs that never fully mature during puberty. The mental abilities are in the low-normal range.

http://www.doctortipster.com/wp-content/uploads/2011/07/turner-syndrome3.jpg
Y chromosome nondisjunction results in YY gametes. When they combine with X gametes, what happens to the XYY zygote?
Jacob syndrome: Normal males but taller and more aggressive

http://www.pathguy.com/ed.gif
Genetic mapping experiments are typically accomplished by carrying out a ____.
Testcross.
What do the telomeres do?
The telomeres ensure that the ends of the lagging strands are replicated correctly.
The information in genes codes for what?
Hereditary traits
What is chromatin?
Chromatin is a complex of eukaryotic chromosomes composed of 60% protein and 40% DNA.
What are the building blocks for DNA and RNA?
Nucleotides
Describe DNA. What type of bond holds the two strands of nucleotide chains together?
DNA is made of two antiparallel strands of nucleotide chains held together by hydrogen bonds between the nitrogen bases.
What makes up nucleic acids?
Organic nitrogen bases, sugar, and phosphate.
Which nitrogenous base is used by RNA?
Uracil
What bond holds one nucleotide with the next within the nucleic acid chain?
A phosphodiester bond.
What is a phosphodiester bond?
A chemical bond connecting one nucleotide with the next one along the nucleic acid chain (phosphate group of one with hydroxyl group of another).
What is the role of the hydrogen bonds in DNA structure?
Hydrogen bonds hold together two antiparallel strands of nucleotide chains (DNA) by stabilizing complimentary nitrogen bases.
How many hydrogen bonds are between the A-T pair and how many between the G-C pair?
2 between A and T
3 between G and C
By what method does DNA replicate?
Semi-conservative method
What catalyzes the synthesis of a new DNA molecule?
DNA polymerase III
What enzyme is required to remove and replace the primer segments?
DNA polymerase I
What is the role of DNA primase?
DNA primase creates a short RNA primer (required by DNA polymerase III) complementary to the DNA template.
What enzyme unwinds the double helix?
How?
DNA helicase uses hydrolysis of ATP to increase efficiency of unwinding the double helix of DNA in front of polymerase.
Describe initiation.
Initiation is the step in DNA replication in which the replication proteins open up the double helix and prepare for complementary base pairing.
What relieves the torsion strain during DNA replication?
DNA gyrase
What is the role of DNA ligase?
DNA ligase is continuously required during DNA replication to join together fragments of lagging strand; DNA repair.
Describe elongation.
Elongation is the step in DNA replication in which the proteins connect the correct sequence of nucleotides into a continuous new strand.
Chargaff's rules pairs what complementary nitrogenous bases together allowing an equal distribution of weight in the double helix?
A pairs with T and G pairs with C
What is pyrophosphate?
A byproduct of DNA synthesis
When is RNA primer needed?
RNA primer is required for DNA polymerase to begin DNA replication.
Okazaki fragments are involved in what kind of synthesis on which strand?
Discontinuous synthesis
Lagging strand
New bases are always added to which end during replication, 5' or 3'?
3'
A new DNA leading strand goes in which direction, 5' to 3' or 3' to 5'?
5' to 3'
What are the basic steps in DNA replication?
Two strands separated;
each strand is used as a template for making a new duplex;
synthesis on each strand is in the opposite direction;
each nucleus contains one strand of the original DNA and one strand of the newly synthesized DNA.
The primosome consists of what?
Primase, helicase, & accessory proteins
The replisome consists of what?
Large macromolecular assembly consisting of primosome & complex of 2 DNA pol III enzymes.
What is the replication fork?
Site of the opening of the DNA strands where active replication occurs.
How is time optimized during eukaryotic DNA replication?
There are multiple origins of the replication from each chromosome, which results in multiple replications.
Describe termination.
The step in DNA replication in which two replication forks moving in opposite directions meet.
What is the role of DNA polymerase I?
Erases primer & fills gap; makes first repair of mistakes made during DNA replication.
What are the steps in synthesis of the lagging strand?
Primase adds RNA primer ahead of 5' end, DNA polymerase III adds nucleotides to primer until gap is filled in, DNA polymerase I replaces primer with DNA nucleotides, and ligase seals the gap.
Who was Watson and Crick?
They proposed the first double helix model of DNA.
The Central Dogma shows what pathway resulting in what product?
transcription & translation = DNA --> RNA --> polypeptides/proteins
What are the building blocks for DNA and RNA?
Both DNA and RNA are made of nucleotide building blocks.
A nucleotide consists of what?
The nucleotides are composed of 5 carbon sugars, phosphate, and nitrogen bases.
What is a structural gene?
An organized unit of DNA sequences that enables it's information to be transcribed into RNA and ultimately results in the formation of a functional product.
What does a nonstructural gene produce?
Nonstructural genes produce transfer RNA and ribosomal RNA therefore they are never translated.
Describe a ribosome.
Large rRNA/protein aggregate residing in cytoplasm.
What is a ribosome's function?
Makes proteins from information on mRNA.
Gene expression consists of what?
Expression consists of two phases, transcription and translation.
What does the process of transcription entail?
Producing an RNA copy of the information in DNA.

Transcription is the DNA-directed synthesis of RNA by the enzyme RNA polymerase. The process used the principle of complementarity to use DNA as a template to make RNA.
What enzyme initiates transcription?
RNA polymerase.

But it needs the addition of a sigma subunit in order to become a holoenzyme in order to initiate synthesis.
What does RNA polymerase bind to?
The promoter.

The binding of RNA polymerase to the promoter is the first step in transcription. Promoter binding is controlled by the sigma subunit of the RNA polymerase holoenzyme, which recognizes the -35 sequence in the promoter on the DNA and positions the RNA polymerase at the correct start site, oriented to transcribe in the correct direction.
So transcription begins and ends at what DNA sites?
Begins: start site
Ends: terminator site
Which strand of DNA is complementarily copied and which strand is not copied ?
Complementarily copied: DNA template

Not copied: coding strand
DNA's complementary purine-pyrimidine relationship of adenine:thymine corresponds to RNA's complementary purine-pyrimidine relationship of adenine: _____
DNA's complementary purine-pyrimidine relationship of adenine:thymine corresponds to RNA's complementary purine-pyrimidine relationship of adenine: uracil
What does the process of Translation entail?
Translation ses information encoded in a portion of the mRNA to guide the ribosome into making a polypeptide.
What components participate in this process of translation?
Translation entails the participation of mRNA, tRNA, translation factors, ribosome and is energized by hydrolysis of GTP.
RNA polymerase is to transcription as ____ are to translation.
RNA polymerase is to transcription as ribosomes are to translation.
RNA is synthesized from (5'-3') or (3'-5').
RNA is synthesized from 5'-3'.
Transcription from nuclear DNA (eukaryotic template strand) results first in ____.
transcription from nuclear DNA (eukaryotic template strand) results first in pre-mRNA.
Pre-mRNA is processed into functionally active mRNA which moves from ____ to ___.
pre-mRNA which is then processed into functionally active mRNA which moves from the eukaryotic nucleus to ribosomes in the cytoplasm.
Which type of RNA brings the specified amino acids to the ribosome as it builds the polypeptide?
Transfer RNA, tRNA
Why are there only 45 tRNA anticodons when there are 64 mRNA codons?
Some tRNA anticodons are able to recognize more than one mRNA codon.
tRNA acts as an intermediary between an ___ and an ___.
tRNA acts as an intermediary between an mRNA codon and an amino acid.
How many different aminoacyl-tRNA synthetases are there in humans?
20
What do aminoacyl-tRNA synthetases do?
Catalyzes the attachment of amino acids to tRNA.
Where is rRNA found?
hhat does it do?
Inside ribosomes, assembles polypeptides
Describe the activity of bacterial RNA polymerase.
It binds the promoter region of a gene.
It is bound to a sigma factor during initiation of transcription.
It synthesizes RNA.
It catalyzes the addition of nucleotides to the 3′ end of a growing RNA strand.
It dissociates from the DNA at the terminator.
Two differences between RNA polymerase in prokaryotes and in eukaryotes?
1 similarity?
1. There is only one bacterial RNA polymerase, and at least 3 in eukaryotes' cytoplasm.
2. There is only one Sigma factor in bacteria, and eukaryotic RNA polymerase II requires 5 general transcription factors.

1. Both bacterial and eukaryotic RNA polymerase add the nucleotides to the 3' end of the growing RNA strand.
What enzyme starts transcription?
RNA polymerase II.
What is the role of the promoter sequence in DNA?
The promoter directs the polymerase to the template strand and to the correct direction to move.
What is the core promoter?
The TATA box
RNA is synthesized in the ___ direction, moving along DNA in ___ direction.
RNA is synthesized in 5' to 3' direction, moving along DNA in 3' to 5' direction.
Eukaryotic post-transcriptional modifications to pre-mRNA to produce mature mRNA takes place in the ___.
Eukaryotic post-transcriptional modifications to pre-mRNA to produce mature mRNA takes place in the nucleus.
What happens during eukaryotic post-transcriptional modifications to pre-mRNA to produce mature mRNA?
Splicosomes remove introns from the primary transcript and reattach exon areas.

Also, methylated GTP to 5' end (5' cap) and long chain of adenine residues to 3' end (3' poly-A tail)
What is a splicisome?
The spliceosome is the large complex of snRNPs that excise intron loops.
What is the difference between introns and exons?
Introns (noncoding) are portions of mRNA transcribed from eukaryotic DNA that is removed by enzymes (RNA splicing) before the mature mRNA is translated into protein.

An exon (coding) is a segment of DNA that is both transcribed into RNA and translated into polypeptide
One amino acid is specified by how many nucleotides in a sequence?
Three
What does it mean when the genetic codes is referred to as degenerate?
Since more than one codon can specify the same amino acid, the genetic code is referred to as degenerate.
Each codon codes for what?
Amino acids
What is the start codon and what are the stop codons?
Start: AUG
Stop: UAA, UAG, UGA; nonsense codons
What are release factors?
Release factors are needed to recognize the stop codon and disassemble the translation machinery.
How many unique mRNA codons can be created from the 4 different RNA nucleotides?
64
What are the principles for genetic code operations?
1. All 4 of the nucleotide bases must be used

2. Each combination of any 3 nucleotides can act as a codon

3. A particular codon (found on mRNA) always specifies the same amino acid.
What makes up the initiation complex?
The initiation complex consists of the small ribosomal subunit; mRNA; tRNA with methionine; and three initiation factors.
What molecule supplies the energy for initiation of translation?
Initiation requires input of energy through GTP hydrolysis.
What does tRNA do?
tRNA carries a specific amino acid to free, single-stranded -OH end (3') of a growing polypeptide chain.
What is an anticodon?
The anticodon is a sequence on tRNA that is complimentary to a three-base sequence on mRNA.
What are the steps to move from a DNA triplet code to the tRNA anticodons?

Example?
You would need to go from DNA triplet to mRNA triplet to tRNA triplet.

Example:
DNA: ATG to mRNA: UAC to tRNA: AUG (so DNA and tRNA are the same except for substitution of U for T in the tRNA)

DNA --> mRNA --> tRNA
ATG UAC AUG
What attaches specific amino acids to tRNA molecules?
Aminoacyl-tRNA synthases
Where does the tRNA anticodon bind to the mRNA codon?
Site A on the ribosome
Where does the tRNA adds its amino acid to growing polypeptide chain via peptide bond?
Site P on the ribosome
Where does tRNA (without amino acid) go before exiting ribosome?
Site E on the ribosome
The A, P, and E sites are found on what?
What is the role for each site?
Ribosomes.

A: where the tRNA anticodon binds to the mRNA codon

P: where the tRNA adds its amino acids to the polypeptide chain

E: where the tRNA goes before exiting the ribosome
What makes up the protein synthesizing machinery?
mRNA, tRNA, ribosomes, initiation factors, amino acids
What are introns? When are they removed?
Introns are intervening sequences of non-coding DNA.

Put onto the pre-mRNA when transcribed but must be removed before mature mRNA codes for protein synthesis.
What are exons?
Coding sequences of DNA
What are splicesomes?
A splicesome is a complex responsible for splicing, or removal, of introns
What is gene regulation?
The cells' ability to control their level of gene expression.
What are proteins only produced at certain time and in specific amount?
Structural genes
What are unregulated genes and have essentially constant levels of expression?
Constitutive genes
How does the organization of genes differ in prokaryotes and eukaryotes?
Prokaryotes: genes are grouped for common functions

Eukaryotes: genes are organized individually
Cell differentiation leads to cell with same genome but different ___.
Cell differentiation leads to cells with same genome but with different proteomes (set of expressed proteins)
Activators bind to DNA to ___ or to ___.
Activators bind to DNA to increase transcription or to turn on a gene.
What is the most common mechanism for gene expression regulation?
Transcription control
When an activator (regulatory transcription factor) binds to DNA and increases the transcription of a gene, it is imposing ____ control.
When an activator (regulatory transcription factor) binds to DNA and increases the transcription of a gene, it is imposing positive control.
What possess DNA binding motifs that allow them to bind to bases of DNA at the major groove?
Regulatory proteins
What regulate gene transcription by binding a regulatory protein?
Effector molecules
What is the site immediately in front of promoter region?
Operator
Regulatory proteins (repressors imposing negative control) can bind to ___ to reduce or shut off transcription
Operator
The ____ region of DNA is where general transcription factors are required for proper binding of RNA polymerase to the DNA helix for transcription to be initiated.
The promoter region of DNA is where general transcription factors are required for proper binding of RNA polymerase to the DNA helix for transcription to be initiated.
What binds to DNA in the vicinity of the promoter and imposes negative control by inhibiting transcription?
Repressor
What is the cluster of functionally-related genes encoded into a mRNA molecule?
Operon
Control strategies in prokaryotes are geared to adjust to ____.
Control strategies in prokaryotes are geared to adjust to environmental changes.
Control strategies in eukaryotes are aimed at ___.
Control strategies in eukaryotes are aimed at maintaining homeostasis.
The most common DNA binding motif is the ___.
The most common DNA binding motif is the helix-turn-helix.
Most common mechanism for gene expression regulation?
Transcriptional control
What is the mRNA that contains the coding sequence for two or more structural genes?
polycistronic mRNA
What is the DNA region that contains genes for use of lactose as energy source?
lac operon
The lac operon contains three structural genes: __, __, __.
lacZ, lacY, lacA