Exam 2- Modification of Medel and Replication Flashcards
What is Incomplete Dominance?
Phenotype of heterozygote is intermediate between the homozygotes and can be on a continuum
What is Codominance?
Phenotype of heterozygote is a mix of both homozygotes
Is Blood Type Determined by 1 or More Alleles?
Multiple Alleles
What are the Possible Genotypes of Type A Blood?
AA or AO
What are the Possible Genotypes of Type B Blood?
BB or BO
What are the Possible Genotypes of Type AB Blood?
AB
What are the Possible Genotypes of Type O Blood?
OO
What Blood Types can A Blood Receive?
A or O
What Blood Types can B Blood Receive?
B or O
What Blood Types can AB Blood Receive?
A, B, AB, or O
What Blood Types can O Blood Receive?
O
What is Lethality?
Sometimes specific alleles can be lethal, acquiring two copies of this allele will cause death in the individual
What is Pleitrophy?
A mutation in a single metabolic enzyme involved in converting the amino acid sequence phenylalanine to tyrosine.
What Results from Phenylketonuria?
- Phenylalanine accumulation
- Loss of tyrosine (loss of melanin)
- Neuronal damage
- Intellectual disability
What is Incomplete Penetrance?
Genotype does not always produce the expected phenotype
What is Variable Expressivity?
The degree to which a trait is expressed
What is Epistasis?
Mutation on multiple genes that affect Phenotype. 1 gene has the ability to mask the effect of the other
What Causes Mutant Phenotype?
- Several mutations in one gene
2. Several different mutations in different genes involved in a phenotype
What is a Complementation Test?
Crossing homozygous recessive mutants to produce hybrids to determine if the phenotype is caused by mutations in the same gene
What is Recessive Epistasis?
An allele at one locus masks the expression of an allele at a second locus.
What is an Example of Pleitrophy?
Phenylketonuria where a mutation in a metabolic enzyme involved in converting phenylalanine to tyrosine occurs
What is an Example of Incomplete Penetrance?
Polydactyl individuals with an extra digit
What is an Example of Epistasis?
Lab Coat Color
What are the arms of a Chromosome Called?
P arm on top
Q arm on bottom
How Many Chromosome Pairs do Humans Have?
23 Pairs
How are Diploid Organisms Chromosomes Organized?
2 pairs of chromosomes organized as homologous pairs
What is Chromatin?
DNA + Nucleoproteins
What Happens at the Centromere of a Chromosome?
The Kinetochore forms and the spindle microtubules attach and separate the sisters
What is the Telomere?
The end of the chromosome where some segments of DNA are repeated to act as a buffer for the actual DNA. Eventually telomeres shorten and the cells division stops
What does Chromatin do for Cell Division?
Condenses into visible chromosomes
What Chromosome Condensing Happens During Interphase?
DNA wraps around histone proteins
What Chromosome Condensing Happens During Prophase?
DNA wrapped around histones wraps into chromosomes
What is the Nucleosome?
8 histone proteins that DNA wraps around
What are the 8 Histone Proteins?
H2A H2B H3 H4 with 2 copies of each
What Happens to Condense DNA After Histones Wrap DNA?
Solenoid fibers form the “30 nm fiber” as the H1 histones form a ring together
What Happens to Condense DNA After the 30 nm Fiber?
Loops form to create the 300 nm fiber
What Happens to Condense DNA After the 300nm Fiber?
The DNA condenses further into the 250 nm fiber of visible chromosomes
What is Heterochromatin?
Densely packed DNA with fewer genes expressed
What is Euchromatin?
Less compacted DNA that is actively transcribed
What does N Represent?
Number of Different Chromosomes (Haploid Set)
What is 2N?
Total number of chromosomes
What are the Phases of the Cell Cycle?
M, G1, S, G2
mitosis, growth 1, synthesis, growth 2
What Happens at the Metaphase Checkpoint?
Pass if all chromosomes are on mitotic spindle
What Happens at the G1 Checkpoint?
Pass if cell size is adequate
What Happens at the S Checkpoint?
Pass if DNA is replicated successfully
What Happens at the G2 Checkpoint?
Pass if cell size is adequate
What do Cohesion Proteins do?
Keep sister chromatids together during prophase, despite the pressure at the kinetochore
What Does Separase do?
Breaks cohesion polypeptide bonds and creates chromosome disjunction
What Cell Cycles Phases are a Part of Interphase?
G1, S, and G2
What Happens During Prophase?
Chromosomes are paired up
What Happens During Metaphase?
Spindle fibers line chromosomes up
What Happens During Anaphase?
Sister chromatids are pulled apart
What Happens During Telophase?
Cell pinches in the middle
What are the Phases of Mitosis?
Interphase, Prophase, Metaphase, Anaphase, Telophase
What does Helicase do?
Breaks H bonds between nucleotides and the complementary strand
What does DNA Polymerase 3 do?
Builds DNA 5’-3’
What Does Topoisomerase do?
Holds the strands tight so they do not unwind
What does Primase do?
Makes RNA primers for DNA polymerase
What do Single Strand Binding Proteins do?
Stop single strand exposure from causing self-attachment
What does DNA Polymerase 1 do?
Replaces RNA in primers with DNA
What does Ligase do?
Seals the backbone
What Would Happen if DNA Polymerase 1 lost 3’-5’ Exonuclease Activity?
No proofreading would occur and nucleotides could be placed incorrectly. this would caused increased mutations
What Would Happen if DNA Polymerase 2 lost 5’-3’ Polymerase Activity?
RNA would not be converted into functional DNA and DNA would not be placed down. Transcription would not be able to long-term work, there would be large gaps in the DNA
What is Euploidy?
Any number of sets of chromosomes
What is Polyploidy?
A cell having more than two sets of chromosomes
What is Aneuploidy?
Variations in the number of single chromosomes, one chromosome more or less than the diploid number
What is Nondisjunction?
Failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, resulting in abnormal distribution of chromosomes in the daughter nuclei
What is Down Syndrome?
Trisomy in the chromosome 21
What is Crossing Over?
When genes are transferred between homologous chromosomes, resulting in allele combinations that are different from either parent
What are the 2 Situations for Meiotic Recombination?
Independent Assortment at the metaphase plate
Crossing over of genes on non-sister chromatids
What is the Recombinant?
The offspring that has different alleles from either parent
What are Parental Types?
Phenotypes that reflect a previously existing parental combination of genes that is retained during gamete formation
What are Recombinant Types?
Phenotypes reflecting a new combination of genes that occurs during gamete formation
How do you Tell if Genes are Linked?
If the ratio of alleles differ from 9:3:3:1, the genes are linked on the same chromosome
What Percentage of Offspring Alleles are Parental and What Percentage are Recombinant? Why?
Parents > 50%
Recombinant < 50%
Because crossing over does not happen all of the time, it is more rare than the regular parent alleles forming
What are the 2 Hybrids That Can be Created When 2 Genes are Linked?
Cis Dihybrid- AB/ab dominant on the same homolog
Trans Dihybrid- Ab/aB dominant on the opposite homolog
How do you Calculate the Recombination Frequency?
Total # of Recombinants % Total # of Progeny
*100
What Controls How Often Crossovers Occur Between Genes?
The distance between the genes. The recombination frequency is proportional to the physical length of DNA between the two genes on the chromosome
What is a Linkage Map?
Using the frequency of recombination to map the genes relative locations on a chromosome
What do Linkage Maps Tell us?
The distance between genes of interest
What is cM?
Linkage map unit- unit of measure of recombination frequency, 1cM=1% recombination frequency
What is the Null Hypothesis of a Chi Squared Test?
The genes are not linked and the observed values are not different enough from the expected
What is the Expected Ratio of Offspring for a Testcross?
1:1:1:1
What is the Degrees of Freedom?
of classes - 1
What does the Goodness of Fit Test Measure?
If the difference between observed and expected results are due to chance or something else at work
What are Inversion Heterozygotes?
Diploid organisms in which one member of a pair of chromosomes is inverted in gene sequence, and the other is normal.
What Phenotype do Inversion Heterozygotes Have?
Normal
Where do Inversions Occur?
Breakpoints in DNA
What Happens During Inversion?
DNA is disrupted and function of gene is disrupted or fused. No DNA is lost or gained, so it is seen as balanced.
What forms Inversion Loops?
Paracentric and Pericentric Chromosomes
What Happens when Crossing Over Happens Inside the Inversion Loop with Paracentric Chromosomes?
dicentric and acentric chromosomes are formed. Dicentric chromosomes break randomly, while acentric chromosomes are lost. RESULTS IS VIABLE AND NONVIABLE GAMETES 50:50 RATIO
What Appears Where on an Inversion Loop?
The inverted DNA sequence is found inside the loop, but the normal DNA is found outside the loop
What is the Difference Between Paracentric and Pericentric Chromosomes?
In Paracentric Chromosomes, the centromere location changes, while in Pericentric Chromosomes, the centromere location does not change. Paracentric Chromosomes result in dicentric and acentric chromosomes, while pericentric has one allele inserted in one chromosome,and then deleted in one chromosome
How do you Know Which is the Dicentric Chromosome?
2 Centromeres
How do you Know Which is the Acentric Chromosome?
No Centromeres
What Happens to the Acentric Chromosome
It is lost
What Happens to the Dicentric Chromosome?
Dicentric bridge forms, causing the chromosome to break randomly into two
What is Triploidy?
Presence of an additional set of chromosomes
What is a Translocation?
If a chromosome undergoes DNA breaks and the region of once chromosome can reattach to a non-homologous chromosome
What is a Balanced Translocation?
Where equal parts of the chromosome are switched so they remain the same size
What is a non-balanced Translocation?
When Chromosomes unequally switch DNA so they are no longer the same size
What is a Robertsonian Translocation?
Two non-homologous chromosomes fuse, reducing chromosome number and creating an extremely large and a potentially very small chromosome
