Genetics Flashcards
How are chromosomes ordered for a Karyotype?
From larges to smallest with the sex chromosomes last
Which chromosome number are the sex chromosomes?
Number 23
What is an autosome?
The first 22 chromosome pairs in a karyotype
What are 2 traits located on the same chromosome found?
Linked genes
What is a section of DNA that controls a trait?
Gene
What is a barr body?
Created when one of the X chromosomes in females is inactivated during embryonic development (about the 100 cell mark)
Are linked genes independently assorted?
No as they are on the same chromosome and therefore will not be seperated unless a cross over during miosis can change this as they could end up on a non-sister chromatid
What allows cells to focus on only transcribing genes relative to their function?
Epigenetics
What is the result of an extra chromosome?
Trisomy of that chromosome
What does epigenetics affect?
The gene expression by allowing/preventing genes to be read
Which bases are bonded together by a double bond?
Adenine and thymine
What is the phenotypic ratio?
Ratio for expressing the strait, and can be represented as a ratio or %
What is Patau Syndrome the result of?
Trisomy 13
What is chromatin?
An indistiguishable mass of chromosomal material and its associated proteins contained within the nucleus
What is it called when heterozygotes show both dominant and recessive alleles?
Co-dominance
What is a pair of chromosomes that are the same size and code for the same informatoin?
Homologous chromosomes
What is ABO blood typing so unique?
There are multiple alleles and codominance
Albinism is caused by a recessive allele. An albino child is born to parets in which one is normally pigmented and the other is albino. What is the probability of future children also being albino?
50%
Red-green colourblindness is a sex linked trait. Eye colour is controlled by multiple alleles (brown, green, and blue). Brown is dominant over green, which is dominant over blue. A green-eyed, normal vision man wants to have children with a blue-eyed, normal vision woman. The woman’s father was colourblind. The man’s parents had brown eyes and blue eyes. Determine the probability the couple will have a son with green eyes and colourblindness?
1/8 chance or 12.5%
What is condensed chromatin that is only seen during cell division?
Chromosomes
What is represented by Aa genotype?
Heterozygous
What blood type is a universal recipient?
AB
What are DNA instructions that are kept? (the useful pieces of DNA)
Exons
What is the length of DNA wrapped around a histone protein?
Nucleosome
What will allow the alleles for 2 linked genes to appear to assort independently?
Recombination
Checkered chickens show white and black feathers. A white chicken is crossed with a checkered chicken. Determine the probability to the different phenotypes of the offspring.
50% - white
50% - checkered
What makes DNA easier to read?
Acetylation (addition of an acetyl group)
Who took the first X-ray picture of DNA and was able to meausre the distances between atoms and the helical structure?
Rosalind Franklin
What is an amniocentesis?
A sample of amniotic fluid to determine karyotype to test for genetic conditions and birth defects; generally done about 15-20 weeks gestation
If 30% of the nucleotides was adenine in a sample, how much cytosine would there need to be?
20%
Because DNA replication will result in two double helices produced, each having an original strand and a new strand, what process do we call it?
Semiconservative process
What is the phenotype?
A description of the characteristic (either expressing or not expressing specific traits)
Which bases are bonded together by a triple bond?
Cytosine and guanine
What are sex linked or X-linked characteristics?
The trait is carried on the X chromosome and there is no copy on the Y chromosome
What changes when you put a sex linked or X linked trait into a punnet square?
The allele goes as a superscript on the X, nothing goes on the Y as it does not carry an allele
What is Edwards Syndrome the result of?
Trisomy 18
What enzyme during DNA replication unzips the DNA by breaking the hydrogen bonds between the bases?
DNA Helicase
What is a locus?
The place each gene is located on the homologous chromosomes
What is generally the result of a monosomy?
Failure during embryonic development
Gene Combinations - Recombination Frequency A/B - 2.5% A/C - 3.0% B/C - 5.5% B/S - 5.5% A/S - 8.0% C/S - 11.0%
Map out these linked genes
C———A——–B—————-S
Can’t have pictures on the free version so excuse the crappy drawing lol
What did Chargaff discover and what is Chargaffs rule?
He determined there were four nucleotides that come in pairs (adenine and thymine; cytosine and guanine)
There had to be an equal amount for both parts of the pair and all 4 total 100%
What is a genotype?
A description of the alleles
A red flower is crossed with a white flower and you end up with a flower that is both red and white. What is this called?
Co-dominance
What is the purpose of DNA gyrase?
Helps with the unwinding of DNA
What is the result of a missing chromosome?
Monosomy of that chromosome
What generates short RNA primers on the strand of DNA during replication?
RNA or DNA Primase
What is the DNA section between histone groups?
Linker DNA
What are introns?
Garbage runs of information between useful bits of DNA (I think of them as introns - in between the useful stuff)
Snap dragon flowers can be white, red, or pink. A pink snap dragon is crossed with another pink snapdragon. Determine the probability of the different phenotypes of the offspring.
25% - white
25% - red
50% - pink
A cross of a homozygous recessive purple-eyed, vestigial winged fruit fly (aabb) with a heterozygous normal-eyed, normal-winged fruit fly (AaBb) yielded the following results:
46% - purple, vestigial
42% - normal, normal
6% - normal, vestigial
6% - purple, normal
Both genes are found on the same chromosome. What is the EXPECTED outcome for linked gene? Which of the offspring are recombinants? What is the recombination frequency for these two genes?
The EXPECTED outcome is ONLY offspring that have the same genotype as the parents, so we would only expect normal/normal and purple/vestigial
Recombinants are offspring that DO NOT have the same genotype as the parents, so in this case that is the normal/vestigial and purple/normal
Converting percentage to frequency (frequency is always between 0 and 1) requires you to divide the percentage by 100 so 12% equals a frequency of 0.12
When is a recessive trait expressed?
When an individual is homozygous recessive for the trait
What is needed before DNA polymerase can add nucleotides to the old strand of DNA?
primers
What blood type is a universal blood donor?
O
Who discovered that DNA was the genetic material and not proteins?
Alfred Hershey and Margaret Chase
They worked with the viruses that were just DNA in a protein coat and infected bacteria. They used radioactive isotopes to find out that it was DNA and not the protein that was injected into the bacteria.
What is represented by AA genotype?
Homozygous dominant
What is a carrier?
A parent that is heterozygous for a recessive disease but can pass the recessive allele to their offspring
What is a genotypic ratio?
Ratio for each gene type, can be represented as a ratio or %
What can be used to map the relative locations of the genes on the chromosome?
Recombination frequency
What is used to predict possible variations in offspring?
Punnett Square
What is the job of DNA Polymerase?
Join free nucleotides to the old strand and proofreads to fix mistakes
What is Turner Syndrome?
Monosomy of the sex chromosomes (only one X chromsome and no Y chromosome)
In humans, polydactyly (extra digits) is caused by a dominant allele, while albinism is caused by a recessive allele. A 5 digit, normally pigmented parent has children with a polydactyl, albino parent. Their first child is albino with 5 digits. Determine the probability of other phenotypes for future children.
25% - polydactyl, normal pigment
25% - 5 digits, normal pigment
25% - polydactyl, albino
25% - 5 digits, albino
How are barr bodies one giant example of epigenetics?
The condensing of the X chromosome makes the genes inaccessible, which is inactivating it, just like regular epigenetics due to certain areas of DNA around a bundle of histones
What is Down Syndrome the result of?
Trisomy 21
What makes DNA harder to read?
Methylation (addition of a methyl group)
What is a dominant allele and what is it represented by?
Overpowers the recessive alleles, represented by a capital letter
What is X inactivation?
About the 100 cell mark (5 day embryos) one of the X chromosomes in females deactivates, definitely interesting but more research is still needed
What is a trait governed by multiple genes?
Polygenic traits
Which enzyme seals breaks in the sugar phosphate backbone?
DNA Ligase
What is non-disjunction?
Division of homologous chromosomes and/or sister chromatids does not occur correctly leading to some gametes being produced missing a chromosome and others with an extra chromosome
What is it called when the genes themselves do not change, but access to them changes, making them inaccessible to proteins that would normally transcribe?
Epigenetics
What type of genetic disease affects the males disproportionately from the females?
Sex linked or X linked diseases
What are the alleles involved in ABO blood typing?
IA and IB (the A and B should be superscript due to co dominance)
i (the recessive allele representing O)
What is the +/- that is seen with blood types and what is it named after?
Rh Factor
Named after the rhesus monkey it was first isolated in
What is a variation of a gene called?
Allele
In what type of genetic disease do heterozygous individuals not express the disease?
Recessive diseases
What is an autosomal genetic disease?
The disease trait is not carried on the x or y chromosomes and gender is not a factor
What fragments does DNA ligase bond together?
Okazaki fragments
What is it called when there are mutliple options for a given trait?
Multiple alleles
Which direction does DNA polymerase read DNA?
From the 3 prime and to the 5 prime end of the parent strand
In what type of disease would heterozygous individuals express the disease?
Dominant diseases
Because strands are antiparallel, what does each replication fork result in?
Leading parent strand (open at the 3 end)
Lagging parent strand (open at the 5 end)
What is Klinefelter Syndrome a result of?
Trisomy of the sex chromosomes (XXY)
Which strand of DNA is synthesized continuously during replication and why does this happen?
The leading strand as DNA polymerase follows the unwinding of the DNA
What is it called when heterozygotes for a trait show a blend between the 2 alleles?
Incomplete dominance
What is a change in DNA that can either help or hurt an organisms survival?
Mutation
Three newborns are mixed up in a hospital. The blood types of all parents and newborns are known. Using this information, match the newborn with the parents. Parents 1: Type A and Type B Parents 2: Type O and Type AB Parents 3: Type B and Type O Newborn X: Type A Newborn Y: Type O Newborn Z: Type AB
Parents 1 - Newborn Z
Parents 2 - Newborn X
Parents 3 - Newborn Y
What in genetics is represented by lower case letters?
Recessive alleles
What does mRNA mean?
Messenger RNA
What type of trait results in a gradient rather than distinct categories?
Polygenic traits
Can males be a carrier for sex linked traits?
No, they can only be carriers for autosomal traits
What is the most common result of trisomy?
Failure during embryonic development
How can a female express a sex linked recessive trait?
If her father has the trait and her mother either expresses the trait or is a carreir for the trait as both alleles would have to be recessive for her to express the trait
A cross of a homozygous recessive purple-eyed, black bodied fruit fly (aacc) with a heterozygous normal-eyed, normal-coloured fruit fly (AaCc) yielded the following results: 466 purple/black 454 normal/normal 42 normal/black 38 purple/normal
Determine the recombination frequency of the two genes
Recombination frequency is 80/1000 = 0.08
What is a karyotype used for?
Determining chromosome abnormalities
What are spontaneous mutations?
Random DNA changes with no outside influence
There are 4 different alleles for rabit coat colour. What is this an example of?
Multiple alleles
Who put all of the previous genetics work into the development of the structure of DNA, subsequently winning the nobel prize for their work?
James Watson, Francis Crick and Maurice Wilkins (former supervisor of Rosalind Franklin)
What is represented by aa genotype?
Homozygous recessive
A red flower is crossed with a white flower and the result is a pink flower. What is this an example of?
Incomplete dominance
What is it called when a segment of DNA within a chromosome reverses?
Inversion
Where is the gene information for tRNA coded?
On the mitochondria
What happens after the ribosome subunits come together around the first tRNA molecule?
A second tRNA molecule carrying the second amino acid joins the ribosome complex. A peptide bond forms between the first (always methionine) and the second amino acid. The tRNA carrying the methionine is then released and the mRNA moves one codon down. This continues until a stop codon is reached
What are some causes of induced mutations?
Radiation, chemicals or infectious agents
What is a silent mutation?
A base pair substitution that causes no effect as it still codes for the same amino acid
What are histones?
A group of 8 proteins which DNA wrap around
What does mtDNA stand for?
Mitochondrial DNA
What occurs when a mutagen causes changes to DNA?
Induced mutation
Describe the differences between DNA and RNA.
RNA is single stranded while DNA is double stranded. RNA has uracil instead of thymine. RNA has ribose sugar instead of deoxyribose. RNA is much shorter than DNA. RNA can leave the nucleus and is used as a blueprint for proteins
What is it called when a segment from one chromosome moves to another, nonhomologous one?
Translocation
Why is the lagging strand synthesized discontinuously during replication?
DNA polymerase only moves from the 3 end to the 5 end so it moves opposite the opening of the replication fork. The lagging strand has to wait for small sections to open up at the 3 end and then Polymerase builds in small sections called Okazaki fragments
A template/anti-sense strand of DNA reads
3 - TAC|GCG|CAG|AGC|TAG - 5
What is the coding/sense strand that would result from this?
5 – ATG|CGC|GTC|TCG|ATC – 3
What happens when a stop codon is reached when reading RNA?
The stop codon binds to a proein release factor, which attaches a water. This releases the last amino acid from the tRNA molecule and the protein is released from the ribosome
What acts as structural support when packaging and storing DNA in the nucleus?
Histones
What is the structure of DNA?
Double helix with a right hand twist
Sugar phosphate backbone
Rungs of a ladder are made of of the bases
What is the strand of DNA that is not being used to create the mRNA?
The coding or sense strand
Sometimes also called a complementary strand
What is DNA composed of?
Phosphate group
Sugar deoxyribose
Base (adenine, thymine, cytosine, or guanine)
Which strand of DNA is used to create the mRNA?
The template or anti-sense strand
What process occurs in the ribosomes?
RNA translation and creating of a protein
What is a base pair error that ends up translating to a different amino acid and what does this cause?
Missense; changes the protein structure that is eventually made, affecting its function
In what order are the bases added to create mRNA?
from the 3 end to 5 end of the parent strand
What is a cancer causing agent called?
Carcinogen
What is the promoter?
The special sequence of DNA to which RNA polymerase binds and transcription begins
What is a chromosomal mutation?
Large segments of DNA that are lost, duplicated or moved around the chromosome
Why are there more mistakes to mRNA than DNA and why doesn’t this generally affect the organism?
RNA polymerase does not proofread like DNA polymerase does. While the mRNA may be mistranslated and subsequently may cause issues with the protein it creates, but it will break down and be reabsorbed and is therefore not a permanent change like changes to DNA would be.
What is the 3 base code carried on the tRNA?
anticodon
How do the 2 parts of the ribosome come together?
The small ribosomal subunit binds to the mRNA, once the first tRNA binds to the mRNA, the large ribosomal subunit also attaches. This larger piece holds the amino acids in place so they can be bound together
A template/anti-sense strand of DNA reads
3 - TAC|GCG|CAG|AGC|TAG - 5
What is the protein sequence that would result from this?
Methionine | Arginine | Valine | Serine | Isoleucine
What is always the start codon?
AUG (school always starts at the end of AUGust)
What is a base pair substitution that chagnes the coding to a premature stop code?
Nonsense
What does tRNA stand for?
Transfer RNA
What types of induced mutations damage a fetus or affect fetal development?
Teratogens
A template/anti-sense strand of DNA reads
3 - TAC|GCG|CAG|AGC|TAG - 5
What is the mRNA strand that would result from this?
5 – AUG|CGC|GUC|UCG|AUC – 3
What is the shift called that results from adding or deleting a single base pair?
Frameshift mutation
What is the result of a base pair that gets inserted or deleted into DNA?
Causes extreme missense as all further codon will now be changed; can also cause nonsense if there is now a stop code where there was not one previously
What is the mapping of generational data to determine the likely inheritance patterns?
Pedigrees
What are females represented by in a pedigree?
Circle
What type of inheritance pattern has to have at least one person in each generation to pass down the trait?
Autosomal dominant
How is someone who shows the trait represented on a pedigree?
By a dark circle
In an autosomal dominant trait, can unaffected parents have affected children?
No
What are males represented by in a pedigree?
Square
In what inheritance pattern can 2 unaffected parents have an affected child?
Autosomal recessive
When looking at a pedigree, in generation 1 you see an affected male and unaffected female have 3 children that are also unaffected. In generation 2, you see 2 unafected parents have 2 unaffected children and 1 affected child as well as 2 affected parents having 2 affected children and no unaffected children. What inheritance pattern is this likely to be?
Because 2 unaffected parents had an affected child, this has to be recessive. Unable to tell if it is sex linked based on this information.
What is an autosomal dominant trait?
A trait located on a gene that is on any chromosome other than the X chromosome; inheriting a dominant allele means the individual will express the phenotype trait in question
When looking at a pedigree, you see 2 affected parents that have 2 affected children and 1 unaffected child. What type of inheritance pattern is this likely to be?
Autosomal dominant
What is a sex linked dominant trait?
A gene located on the X chromosome in which the individual will express the trait if they have at least one dominant allele
When looking at a pedigree, 2 affected parents in generation 1 have an affected son and daughter and an unaffected son. 1 affected man has children with an unaffected woman in generation 1 and they have an affected son and an unaffected daughter. The 2 unaffected children in generation 2 have 3 children together, 2 boys and a girl, and all are unaffected. What inheritance pattern is this likely to be?
Has to be dominant as the 2 affected parents had an unaffected child
Not sex linked as the mother is unaffected with a male child that has the condition
What type of inheritance pattern would require an affected female to have an affected father?
Sex linked recessive or autosomal recessive
What type of inheritance pattern can result in two affected individuals having an unaffected child?
autosomal dominant
What are the characteristics of a pedigree showing an autosomal recessive condition?
Trait tends to skip generations
If both parents are affected, all children will also be affected
Two unaffected parents can have an affected offspring (both parents would have to be heterozygous)
If both parents are affected by an autosomal recessive condition, what will happen to their children?
They will all be affected as well
What is a sex linked recessive trait?
Gene found on the x chromosome; females will need to have 2 recessive X chromosomes to express the trait where males only need 1 recessive chromosome as it is not linked on the Y gene
What type of inheritance pattern does the sex-linked dominant trait mimic?
Autosomal dominant, it is indistinguishable so this will not be on the exams. Can determine if it is likely, but it is unable to say for sure which it is.
What are the characteristics of a pedigree showing an autosomal dominant condition?
One person in every generation has to be affected to pass down the trait
An affected offspring has to have at least one affected parent
If both parents are unaffected, all children will be unaffected
Two affected individuals can have an unaffected offspring (both parents would have to be heterozygous)
In what inheritance pattern does an affected offspring have to have an affected parent?
Autosomal dominant
When looking at a pedigree, you see that 1 unaffected parent in generation one; there are no affected individuals in generation 2 or 3; in genration 4, there are 2 affected children (one male, one female) from 2 unaffected gen 3 parents. What is the likely inheritance pattern?
Autosomal recessive
It cannot be sex linked recessive becasue the daughter has an unaffected father
In what inheritance pattern would an affected mother pass the trait onto all of her sons?
Sex linked recessive
In what inheritance pattern does the trait tend to skip generations?
Autosomal recessive
When looking at a pedigree, you see an affected mother and an unaffected father had 2 unaffected daughters and 2 affected sons. One of the unaffected daughters marries an unaffected man and has 3 unaffected children (2 girls and a boy) and an affected son. On of the affected sons has children with an affected woman and all 3 of their children (2 boys and a girl) are affected. What inheritance pattern are you likely looking at?
Because 2 unaffected parents have an affected child, it has to be recessive
Could be se linked as the only femal affected (that didn’t marry in) had an affected father but there isn’t a hugheslly disproportionate amoutn of males so not enough to difinitively say it is sex linked
What is an autosomal recessive trait?
A gene found on any chromosome other than the X chromosome in which a person would have to inherit 2 recessive alleles to express the trait
What is the characteristic would not allow sex-linked dominant to not be ruled out when looking at a dominant inheritance pattern?
Fathers who express the trait will always pass it on to all of their daughters. It cannot be distinguished from autosomal dominant but it can be ruled out, just not distinctly ruled in.
What type of inheritance pattern tends to be seen more in males than females?
Sex linked recessive
