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BIO 235 Exam 2 With 100% Correct Answers 2025/2026, Exams of Biomedicine

American University (AU)Biomedicine

Independent assortment - Correct Answer-Genes assort independently of each other when they are on opposite chromosomes Linkage - Correct Answer-Two genes on a single pair of homologs; exchange occurs between two non-sister chromatids Chiasmata - Correct Answer-Location of exchange of information between chromatids when does crossing over occur? - Correct Answer-prophase I of meiosis How often does recombination occur? - Correct Answer-Very frequently What determines how often genes will cross over? - Correct Answer-Their distance from one another. The closer they are, the less likely they are to cross over. What does it mean when genes are linked? - Correct Answer-they are on the same chromosome; assort independently

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BIO 235 Exam 2 With 100% Correct
Answers 2025/2026
Independent assortment - Correct Answer-Genes assort independently of each other
when they are on opposite chromosomes
Linkage - Correct Answer-Two genes on a single pair of homologs; exchange occurs
between two non-sister chromatids
Chiasmata - Correct Answer-Location of exchange of information between chromatids
when does crossing over occur? - Correct Answer-prophase I of meiosis
How often does recombination occur? - Correct Answer-Very frequently
What determines how often genes will cross over? - Correct Answer-Their distance from
one another. The closer they are, the less likely they are to cross over.
What does it mean when genes are linked? - Correct Answer-they are on the same
chromosome; assort independently
Describe how geneticists detect linkage of a gene - Correct Answer-1. Select true-
breeding lines that are homozygous dominant for one trait & homozygous recessive for
the other trait (ygr ANL / ygr ANL & YGR anl / YGR anl). Parents produce dihybrid F1
population (ygr ANL / YGR anl)
2. Cross the F1 dihybrid with a homozygous recessive (ygr anl / ygr anl). This will result
in an F2 pop. where the dihybrid traits segregate.
3. Cross each F2 individual with a homozygous recessive
How do you determine if the genes are linked or not after performing a test cross? -
Correct Answer-If the ratio is 1:1:1:1, they assort independently and are unlinked
If the ratio for the recombinant class is less than the parental class, you know they do
not assort independently and are linked
Parental class - Correct Answer-original arrangement of alleles on the two
chromosomes (no recombination); came from meiosis unchanged
Recombinant class - Correct Answer-does not have chromosomes passed from parents
How is distance between genes found? - Correct Answer-The farther apart two genes
are located on a chromosome, the higher the probability that a recombinant event takes
place between them
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Download BIO 235 Exam 2 With 100% Correct Answers 2025/2026 and more Exams Biomedicine in PDF only on Docsity!

BIO 235 Exam 2 With 100% Correct

Answers 2025/

Independent assortment - Correct Answer-Genes assort independently of each other when they are on opposite chromosomes Linkage - Correct Answer-Two genes on a single pair of homologs; exchange occurs between two non-sister chromatids Chiasmata - Correct Answer-Location of exchange of information between chromatids when does crossing over occur? - Correct Answer-prophase I of meiosis How often does recombination occur? - Correct Answer-Very frequently What determines how often genes will cross over? - Correct Answer-Their distance from one another. The closer they are, the less likely they are to cross over. What does it mean when genes are linked? - Correct Answer-they are on the same chromosome; assort independently Describe how geneticists detect linkage of a gene - Correct Answer-1. Select true- breeding lines that are homozygous dominant for one trait & homozygous recessive for the other trait (ygr ANL / ygr ANL & YGR anl / YGR anl). Parents produce dihybrid F population (ygr ANL / YGR anl)

  1. Cross the F1 dihybrid with a homozygous recessive (ygr anl / ygr anl). This will result in an F2 pop. where the dihybrid traits segregate.
  2. Cross each F2 individual with a homozygous recessive How do you determine if the genes are linked or not after performing a test cross? - Correct Answer-If the ratio is 1:1:1:1, they assort independently and are unlinked If the ratio for the recombinant class is less than the parental class, you know they do not assort independently and are linked Parental class - Correct Answer-original arrangement of alleles on the two chromosomes (no recombination); came from meiosis unchanged Recombinant class - Correct Answer-does not have chromosomes passed from parents How is distance between genes found? - Correct Answer-The farther apart two genes are located on a chromosome, the higher the probability that a recombinant event takes place between them

Recombinant frequency (RF) - Correct Answer-percentage of the total progeny that are recombinant type 6% RF = ___________ - Correct Answer-6 map units OR 6 centimorgans From a test cross, you observe that there are 350 offspring for each parental genotype and 150 for each recombinant genotype. What is the distance of the recombinant genes? - Correct Answer-30 map units What is one problem with relying on RF in linkage mapping? - Correct Answer-Genetic distance is massively underestimated when genes are father apart Genetic distances are not additive - RF will never be >50% The farther apart they are, the less reliable the numbers are Double-crossover is more likely the further they are from each other Double-crossover - Correct Answer-One crossover will switch the alleles of homologous chromosomes, but another crossover will reverse the effects of the first, restoring the original parental combination of alleles. This leaves you with non-recombinant genotypes even though a portion of the chromosome crossed over Linkage group - Correct Answer-Alleles of different genes that are located on the same chromosome and tend to be inherited together Haplotype - Correct Answer-a group of genes within an organism that was inherited together from a single parent; A group of alleles of different genes on a single chromosome that are closely enough linked to be inherited usually as a unit Phenotypic marker - Correct Answer-mark of position on chromosome that allows you to create a map of the chromosome How are phenotypic markers similar to highway markers? - Correct Answer-They don't change or do anything, they just help you know where you are at How can you calculate the frequency of double crossover (DCO) events? - Correct Answer-product rule If the frequency of a single crossover between A and B is 12%, the frequency for B and C is 18%, what is the frequency of a double crossover between A and C? - Correct Answer-0.18*0.12 = 0. 21.6% Chromosomal Interference - Correct Answer-Crossovers do not occur independently Crossover between A and B decreases the chance of a crossover between B and C

Two of four chromosomes will be normal, one will be longer, one will be shorter Paracentric inversion - Correct Answer-Inversion occurs away from the centromere Results in two normal chromosomes, one with two centromeres, and one with no centromeres What happens to the two abnormal chromosomes from pericentric inversion? - Correct Answer-The chromosome with no centromere will be lost bc the spindle fibers have nothing to grab hold of The chromosome with 2 centromeres will break because one spindle fiber will grab it from one end and another from the opposite end, playing tug of war What happens when inverted chromosomes crossover? - Correct Answer-They do not crossover equally, leaving one part of the chromosome without a centromere. That chromosome is lost bc it has no centromere. Dicentric chromosomes lead to dicentric bridges dicentric bridge - Correct Answer-Structure produced when the two centromeres of a dicentric chromatid are pulled toward opposite poles, stretching the dicentric chromosome across the center of the nucleus. Eventually, the dicentric bridge breaks as the two centromeres are pulled apart. What causes Familial Down-Syndrome? - Correct Answer-Translocation of q are of chromosome 21 (q-) is translocated to chromosome 10 or 14 (q+). This causes there to be three ends of chromosome 21, which heavily affects gene dosage. Translocation carrier - Correct Answer-Individual organism heterozygous for a chromosome translocation metacentric chromosome - Correct Answer-Chromosome in which the two chromosome arms are approximately the same length, which leaves one fragmented chromosome. Person can live without fragment. What happens to translocated chromosomes when they find their homologous pair? - Correct Answer-They form cross-like structures in order to line up correctly. It causes infertility 50% of the time; it depends how the chromosomes line up during metaphase Fragile X Syndrome - Correct Answer-A genetic disorder involving an abnormality in the X chromosome, which becomes constricted and often breaks. If have just a few repeats, the effects are not bad but become worse as the number of repeats increases trinucleotide repeats - Correct Answer-a form of mutation associated with the expansion in copy number of a nucleotide triplet in or near a gene

How do numbers of triunucleotide repeats affect people? - Correct Answer-<50 - unaffected 55 - 230 - pre-mutation

230 disease causing Rearrangement - Correct Answer-2n = 6 Part of one chromosome is passed to its sister chromatid Aneuploidy (trisomy) - Correct Answer-2n + 1 = 7 One set of chromosomes does not have the right number of chromosomes Polyploidy (autotriploid) - Correct Answer-3n = 9 Variation in the number of complete sets of chromosomes Gene dosage is balanced Why is polyploidy used in farming? - Correct Answer-The gene ratios are all equal, but the extra chromosome for each set increases gene dosage making the plants bigger Euploidy - Correct Answer-Condition in which a cell contains the correct ratio of chromosomes types of aneuploidy - Correct Answer-Nullisomy - loss of both members of a homologous pair of chromosomes (2n − 2) Monosomy - loss of a single chromosome (2n − 1) Trisomy - gain of a single chromosome (2n + 1) Tetrasomy - gain of two homologous chromosomes (2n + 2) Primary Down Syndrome - Correct Answer-Caused by the failure of chromosome 21 to segregate properly (nondisjunction) Nondisjuction - Correct Answer-the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei (down syndrome) Are autosomal conditions more severe than sex chromosome conditions? - Correct Answer-Yes bc the extra X chromosomes are made nonfunctional Autosomes carry hundreds of genes Are monosomies lethal? - Correct Answer-Yes, very Autopolyploidy - Correct Answer-a type of euploidy wherein the additional set of chromosomes is derived from a parent or identical parental species Allopolyploidy - Correct Answer-chromosome sets are from two or more species

auxotrophs - Correct Answer-unable to reproduce in minimal medium Carbon-source mutants - Correct Answer-defective in using certain carbohydrates from the environment What composes the bacterial genome? - Correct Answer-one or more circular chromosome & one or more plasmids Transformation - Correct Answer-when bacterial cell dies, DNA is released from cell, & another cell picks it up & takes it as its own Conjugation - Correct Answer-only for plasmids donor cell establishes bridge, passes one strand of plasmid DNA to the recipient cell Transduction - Correct Answer-viruses (phages) when phage infects bacterial cell, it kills that cell & the created phages infect other cells, passing on original cell's DNA Plasmid - Correct Answer-a small ring of DNA that carries accessory genes separate from those of the bacterial chromosome replicates independently Are plasmids essential? - Correct Answer-no but they do provide advantages for the cell such as the ability to make hosts sick F factor (fertility factor) - Correct Answer-conjugative plasmid transferred from cell to cell by conjugation is an episome low copy number plasmid in length Episome - Correct Answer-a genetic element that can exist either as a plasmid or as part of the bacterial chromosome Describe the process of conjugation and the F factor - Correct Answer-F+ cells use appendages called pili to find a F- cell. When they do, they form a bridge between the cells. A single strand of the DNA from the F+ cell will go across the bridge into the F- cell. Hfr cell - Correct Answer-a cell with the F plasmid integrated into the chromosome How is transfer of Hfr different than F? - Correct Answer-Since the F factor in Hfr is integrated into the chromosomes, the recipient cell receives some of the DNA from the chromosome

Describe the process of Hfr transfer from one cell to another - Correct Answer-A cell with integrated F in Hfr will find an F- cell and form a bridge between them. The Hfr cell will begin a rolling-circle replication process starting at the Hfr, sending one strand to the F- cell similar to unwinding tape. The Hfr cell will begin to replicate and the transferred strand will also replicate until it is done and will separate. The newly acquired chromosome fragment will find its homologous pair and crossover, leaving the Hfr and part of the donor cell's DNA in the F- cell. Recipient cell remains F-. interrupted mating technique - Correct Answer-Hfr and F- strains were incubated, and samples were removed at various intervals and placed in a blender. The cells were then assayed for genetic recombination--demonstrated that specific genes of a given Hfr strain were transferred and recombined sooner than others How is distance of genes in bacteria determined? - Correct Answer-comparing their times of entry during an interrupted mating experiment Units of measurement are the minutes What makes up a phage? - Correct Answer-Head - contains nucleotide genome Shaft - made up of proteins Tail fibers - allow it to attach to bacterial cells lytic cycle - Correct Answer-Phage attaches itself to bacterial cell Injects its DNA into cytoplasm Phage DNA directs the synthesis of new phages and degrades host DNA Cell lyses & releases new phages Those phages infect new cells lysogenic cycle - Correct Answer-After phage DNA is in the cytoplasm, the phage DNA can integrate into the host chromosome, creating a prophage This leads to the cell making copies of this chromosome each time it divides, surviving bacterial cell is lysogen The phage DNA can then direct the synthesis of new phages, causing the host cell to lyse Virulent phages - Correct Answer-reproduce strictly through the lytic cycle and always kill their host cells Temperate phages - Correct Answer-phages that use both the lytic and lysogenic cycles Generalized transducing phage p1 - Correct Answer-cuts bacterial chromosome into pieces and can package bacterial DNA into phage particles generalized transducing phage - Correct Answer-transfers DNA derived from any part of the bacterial chromosome

influenza virus - Correct Answer-RNA genome genome is coded into 8 RNA molecules and must have all eight has no envelope bc small enough to endocytosis into cell outside of cell has proteins that bind to receptors on host cells (how we name viruses H1N1) How do viruses evade the immune system? - Correct Answer-Antigenic shift - viruses whose genome are composed of several different RNA molecules can re-assort those RNA molecules & create new strains w/ dynamically new genome characteristics (human, avian, swine form H1N1 swine influenza virus) Antigenic drift - change in viral genome (random mutations) over time through errors that make it no longer recognizable to the immune system