Principles of Genetics - Exam 2 Flashcards

duplications (tandem, displaced, reverse), deletions, inversions (paracentric, pericentric) and translocations (nonreciprocal, reciprocal)

duplicated region immediately adjcacent to original segment

located away from original

inverted segment

in the nucleus

cytoplasm

centromere in the center, chromosome has arms of equal length

centromere displaced towards one end, one short and one long arm

centromere near one end, long arm and a knob

centromere at or near the end of the chromosome

rearrangements, aneuploids, and polyploids

mutations that change the structure of individual chromosomes. Duplications, deletions,

part of the chromosome is doubled. Tandem, displaced, reverse.

heterozygotes have problems in chromosome pairing at prophase I of meiosis, chromosome must loop in order to pair correctly. unbalanced gene dosage.

duplicated region immediately adjacent to original segment

located away from the original

inverted segment

loss of chromosome segment

• depends on which genes were deleted. If area with centromere deleted, homologous chromosomes will not segregate in meiosis or mitosis and will be lost.
• If homozygous usually lethal
• Heterozygotes have defects because of imbalance of gene product, expression of homozygous recessive traits (pseudodominance), or lack of normal function (due to necessity of having 2 copies of the gene) ? haploinsufficient gene

expression of homozygous recessive traits due to deletion

effect of deletion, lack of normal function due to necessity of having 2 copies of the gene

chromosome segment is inverted – turned 180 degrees. Paracentric and pericentric

don’t include centromere (para-next to)

include centromere (peri-around)

• May break gene in two parts, destroying the function of the gene.
• Inversions in meiosis – no problem if homozygous for inversion, but problems with alignment if heterozygous. Must form inversion loop. See pg 155. Crossing over results in abnormal chromosomes; one with two centromeres (dicentric chromatid) and one with none (acentric chromatid) ? gametes not viable

movement of genetic material between nonhomologous chromosomes or within the same chromosome. Nonreciprocal and reciprocal.

increase or decrease in number of individual chromosomes, arise through nondisjunction

• can physically link genes that were formerly located on different chromosomes, can disrupt function of a gene. Reciprocal translocations can create crosslike configurations during prophase I of meiosis including four chromosomes; only about half the gametes turn out to be functional,so the individual has reduced fertility.
• Robertsonian translocation – long arms of two acrocentric chromosomes become joined, leaving the other with two very short arms. The small chromosome often fails to segregate ? reduction in chromosome number

change in number of chromosome sets

loss of both members of a homologous pair of chromosomes

2n-1 loss of a single chromosome

2n+1 gain of a single chromosome

2n+2 gain of two homologous chromosomes

results in trisomy and monosomy. Leaves sister chromatids attached when the cell divides into two. One cell has both chromosomes, the other has none.

results in monosomy, trisomy, and normal cells.

Whole sets of chromosomes fail to separate in meiosis or mitosis Triploids (3n) - tetraploids (4n), pentaploids (5n).

chromosome sets are from a single species

autotetraploid

produces 2n gametes, which fuse with a normal gamete to produce triploid (3n) zygote. Leads to unbalanced gametes with various numbers of chromosomes… when they separate, who knows what the organism will end up with. Often lethal

chromosome sets from two or more species Two similar species provide different sets of genes, which become hybridized. The resulting organism will contain copies of both, and becomes a polyploid (even though it has the same chromosome number as both diploid species and is diploid)

because the chromosomes are not homologous and cannot pair.

enzymes that add or remove rotations from the DNA helix by temporarily breaking nucleotide strands, rotating ends around each other, then rejoining.

undergoes normal process of condensation and decondensation, undergoes transcription

remains highly condensed, all chromosomes have it at centromeres and telomeres

small positively charged proteins that DNA winds around.

simplest level of chromatin structure. Particle consists of DNA wrapped around an octamer of eight histone proteins

two DNA molecules are built using the two strands of original DNA as templates.

5' to 3'... new bases added to 3' OH group

3' to 5'

Because DNA can only be synthesized in the 5' to 3' direction, one of the strands undergoes continuous replication (the leading strand) whereas the other strand undergoes discontinuous replication (lagging strand)

loop forms at growing fork that allows DNA polymerase dimer to synthesize both strands in the ‘same’ direction. Okazaki fragments are joined when DNA polymerase with exonuclease activity removes the RNA primer, simultaneously synthesizes DNA to fill in spot wehre RNA is removed, and the nick is repaired by DNA ligase.

because synthesis requires a primer, each DNA strand would be shorter than the parent… telomerase comes in with an RNA template and adds to the end

Initiation, unwinding, elongation, termination

initiator protein binds to the origin (oriC) and causes short section to unwind. Helicase comes in to unwind more.

synthesizes primers with 3'OH group at beginning of each DNA fragment. Primers are later removed.

proteins include DNA helicase, single-strand-binding proteins, and DNA gyrase

breaks H bonds between nucleotides, unwinds DNA

attach to exposed single strand to protect and keep them straight for replication

a topoisomerase, reduces torque by making a double-stranded break in one segment of DNA, then repairing it. Reduces supercoiling.

DNA is synthesized with use of single strand as DNA template. DNA polymerase and ligase.

DNA polymerase needs a 3’ OH group to add to, so primase synthesizes primers (short stretches of RNA nucleotides that are later removed). In lagging strand synthesis, primers must be synthesized for every fragment.

catalyzes DNA polymerization, uses dNTP to synthesize new DNA

repairs breaks between nucleotides on lagging strand and after primer is removed.

when two replication forks meet, or when it meets the termination sequence.

primase activity, initiates synthesis by creating RNA primer + short string of DNA nucleotides.

completes replication on lagging strand

replicates leading strand

replicates mitochondrial DNA

ends of chromosomes, contain many copies of a short repeated sequence.

can extend ends of chromosome. Contains RNA component and a protein. RNA component has sequence that pairs with overhanging end of chromosome, which serves as a template for DNA synthesis.

DNA contains deoxyribonucleotides, whereas RNA contains ribonucleotides. THe difference is that on the 2' carbon, RNA has an OH group whereas DNA has only a H

Ribose sugar with base attached to 1' carbon, and phosphate group attached to 4' carbon.

sugar, phosphate, and base.

make up ribosome (along with ribosomal protein subunits)

carries coding instructions for polypeptide chains from DNA to ribosome, is the template

primary transcripts, immediate products of transcription within the nucleus, modified before becoming mRNA and going out into the cytoplasm

attaches to a particular amino acid and adds it to the polypeptide chain. Link between coding sequence and the end product: protein

DNA template (Only one of the strands is used as a template) Raw materials (ribonucleotide triphosphates) needed to build a new RNA molecule, Transcription apparatus, consisting of proteins necessary for catalyzing synthesis of RNA

Promoter, RNA coding sequence, and terminator

DNA sequence the apparatus recognizes and binds, next to transcription start site (but is not transcribed itself).

sequence of DNA nucleotides to be copied into RNA molecule

sequence of nucleoties that signals where transcription should end

coding regions

intervening sequences, noncoding regions

genes can move under the right circumstances.

the segment of DNA that moves, contains enzymes it needs to mediate its movement. Insertion to a new place is not specific, so can interrupt genes

short interspersed sequences. Certain type, “Alu” repeats make up 10% of human DNA

long interspersed sequences, 10-15% of the genome, transposition of ancestral sequences. Open reading frame and absence of introns.

gene is transcribed normally, acted on by reverse transcriptase, DNA copy is reinserted randomly into the chromosome.

from alteration of a single nucleotide in the DNA. 2 types: transition and transversion

purine replaced by different purine, or pyrimidine replaced by different pyrimidine

purine replaced by pyrimidine or vice versa.

addition or removal of one or more nucleotide pairs

alters the wild-type allele

changes a mutant allele back into the wild type allele

base substitution that results in a different amino acid in the protein

changes a sense codon (specifies an amion acid) into a nonsense codon (terminates translation)

changes codon to a synonymous codon. Not truly silent because the change can result in different rate of protein synthesis, protein folding, etc.

missense mutation that alters amino acid sequence of protein but doesn’t significantly change function

produces entirely new trait or causes trait to appear in an inappropriate tissue or at an inappropriate timein develppment.

expressed only under certain conditions

insertions or deletions that changes in the reading frame of the gene, therefore altering the amino acid sequence. drastic influence on phenotype. “in-frame insertions or in-frame deletions”

number of copies of a set of nucleotides increase in number

genetic change that hides or suppresses the effect of another mutation. Arise randomly. 2 types: intragenic and intergenic

is in the same gene containing the mutation being suppressed. Ex. If a base is deleted, one may be added later on to restore the rest of the DNA to where it should have been (therefore allowing some of the right amino acids to be coded for)

occurs in a gene other than the one bearing the original mutation.

• depurination - loss of purine base from nucleotide
• deamination - loss of amino group from nucleotide

DNA sequences capable of moving. Often cause mutations by inserting into another gene and disrupting it or by promoting DNA rearrangements such as deletions, duplications, and inversions.

isolating and manipulating DNA, combining from two different sources

• 1. isolate gene of interest,
• 2. digest gene of interest and cloning vector with same restriction enzymes,
• 3. mix and bind together the foreign and plasmid DNA,
• 4. introduce to bacterial cells
• 5. select for transformed cells,
• 6. produce recombinant protein

• 1. origin of replication
• 2. selectable markers - so that the cell containing the vector can be identified
• 3. one or more unique restriction sites into which the gene can be inserted.

target DNA, taq polymerase, nucleotides, primers

• Denaturation of DNA
• Annealing of primers
• elongation of primers (taq polymerase)

contains only genes that are expressed in an organism or tissue

splicing removes the introns from pre-mRNA to make mRNA, which contains only expressed genes.

it means that some of the 20 amino acids are coded for by more than one codon.

promoter, coding region, terminator