DNA
Genetics
Mutations
Punnett Squares
Surprise!
100
In DNA,
_______ pairs with _______
_______ pairs with _______
A pairs with T
G pairs with C
100
Identify the following genotypes as homozygous dominant, homozygous recessive, or heterozygous
Aa
BB
cc
Aa - heterozygous
BB - homozygous dominant
cc - homozygous recessive
100
Original DNA: CAT GGA CAC TAG
Mutated DNA: CAT GGG GAC ACT AG
What type of mutation is this? Where is the mutation located?
Insertion - GG inserted at beginning of second codon
100
Complete the following Punnett Square. Identify the possible phenotypes and genotypes of the offspring.
B = brown eyes
b = blue eyes
BB x bb
4/4 Bb
0/4 Homozygous dominant for brown eyes
4/4 Heterozygous for brown eyes
0/4 Homozygous recessive for blue eyes
100
Mitosis is when...
Cells replicate their DNA and divide in two
200
What is an anticodon?
The tRNA that brings the correct amino acid over to the mRNA to create a protein chain (like an Uber driver)
200
What is the difference between dominant and recessive genes?
Dominant - only one copy of a dominant gene is needed to show a recessive trait
Recessive - two copies of a recessive gene are needed to show a recessive trait
200
Original DNA: GAG CGG AAC TTT Mutated DNA: GAG CGA AAC TTT Will this person have a mutation?
No - it still codes for all of the same amino acids
200
Complete the following Punnett Square. Identify the possible phenotypes and genotypes of the offspring.
R = curly hair
r = straight hair
Rr x rr
2/4 Rr
2/4 rr
2/4 Heterozygous for curly hair
2/4 Homozygous recessive for straight hair
200
Why are there only 20 amino acids but 64 possible combinations?
More combinations per amino acid offer a greater chance for the same amino acid and later protein to form if a mutation were to happen.
300
mRNA: GUC CUG AUU AAG
What amino acids does this DNA strand code for?
Valine - Leucine - Isoleucine - Lysine
300
What makes a dog "purebred"?
If both of its parents are the same type of dog, they will produce more of the same type of dog with the same physical characteristics. If its parents are two different types of dog, they will produce babies that have characteristics of both dogs and look different from the parents.
300
Original DNA: CCC - ACC - AAA - TAT
Orignal amino acids: Gly - Try - Phe - Iso
Mutated DNA: CGC - CAC - CAA - ATA - T
Mutated amino acids: Ala - Val - Val - Tyr
Would the person with the mutated DNA have a genetic disorder compared with the original DNA sequence? How do you know?
Yes - it's an insertion mutation which shifted codons down and now NO amino acids are the same as the original sequence
300
Billy and Sally are getting married. Billy is heterozygous for his tall height, while Sally is short. Create a Punnett Square to show the possible genotypes of their kids - what's the likelihood that their children will be tall like Bill?
2/4 Heterozygous
2/4 Homozygous recessive
50% chance of their kids being tall
300
Is this a dominant or recessive disorder? How do you know?
Dominant: one copy gives you the disease, there are no carriers - so you either have it or you don't
400
How are genes, chromosomes, and DNA related?
DNA consists of nucleotides (A, T, G, C). Genes are large pieces of DNA that code for certain proteins to be made. Chromosomes are large chunks of genes all condensed together around proteins called histones to help them stay organized.
400
What organism would be better to study genetics in: bugs or humans? Why?
Bugs - they reproduce faster so you can see results faster
400
Some mutations are harmful, some are helpful, and most do nothing at all. Please explain how this statement is true.
Most of us have mutations in our bodies but they still code for the correct amino acid, so the proteins our bodies produce aren't changed. Some mutations code for the wrong amino acid, and a lot of these mutations wind up being harmful since the right protein can't get made. Some mutations are actually helpful and help move the species forward through evolution, but these instances are rare.
400
Two giraffes have a new baby. The mom is a hybrid for her large ossicones (horns) while the dad is a purebred for his. Create a Punnett Square to show the probability of their giraffe baby having large ossicones.
Hh x HH
2/4 Homozygous dominant
2/4 Heterozygous
4/4 Large ossicones
400
Why do some of us look like our biological parents and other people look nothing like their biological parents?
It is RANDOM what genes get passed onto the next generation. You have two copies of each gene you have, and it's chance (think of the coin flip) as to which genes are present in which egg/sperm cells. You can pass on a trait you didn't even know you had if you're heterozygous!
500
What happens during transcription?
A copy of the DNA from the target gene is made using mRNA inside the nucleus. The mRNA strand then leaves the nucleus for translation to happen.
500
Why is a person's genotype ultimately more important than their phenotype when discussing genetics?
A person can be heterozygous and carry a recessive trait without knowing it, and then the recessive trait can pop up in future generations. It's more important to know a person's genotype because that tells us what two alleles they have - what they look like won't necessary tell us the whole picture.
500
How can mutations allow a species to evolve? (We haven't talked about this yet but I want to know your thoughts)
If a mutation is beneficial for an organism, it will help that organism survive better which means it will live long enough to pass on that mutation. Eventually, organisms without that mutation won't live as long as organisms with the mutation and pretty soon every new organism of that species will have the mutation. Once a mutation becomes a normal part of a species' DNA we have evolution.
500
Mickey Mouse and Minnie Mouse finally had a baby! Mickey Mouse and Minnie Mouse are both heterozygous for their large ears. Their baby however has tiny ears - did the Disney World hospital make a mistake? Create a Punnett Square to help explain your answer.
1/4 Homozygous dominant
2/4 Heterozygous
1/4 Homozygous recessive
75% chance big ears
25% chance small ears
No, the hospital didn't make a mistake - while unlikely, it is possible for these two to have a baby with small ears!
500
In this pedigree, is the disorder X-linked or not? How do you know?
Not X-linked - a female has the disorder too