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Heredity
DNA
Heritability and Applied Behavior Genetics
Evolution and Phylogeny
100

Heredity relates the passing of ___ pairs of _______ from one generation to the next.

23 pairs of chromosomes

100

What is DNA made of?

  • bases (“rungs”): adenine, thymine, guanine, cytosine (a-t pair and C-g pair)
  • phosphate/sugar bonds (“sides”)
100

Describe the main difference between Heredity and Heritability.

Heredity focuses on the passing of genetic material from one generation to the next. 

Heritability focuses on the expression of traits based on the interaction between genes and environment. 

100

Why is human evolution still only a theory rather than law or fact?

We cannot prove human evolution in a laboratory setting because it takes too long! However, there is significant evidence in nature and related lab studies: 

  • experimental evidence from bacteria and other simple organisms
  • evidence from the real world - fossils showing ancestors, geology showing environmental pressures
200

Explain why inheriting the genes for thick curly hair does not affect the likelihood that you will inherit genes for liking the taste of cilantro. 

law of independent assortment: inheritance at one locus is not affected by inheritances at another locus

200

How do cells use DNA to create proteins?

  • transcription of DNA to mRNA (happens in the cell nucleus) - for mRNA T is replaced with U - RNA splicing
  • translation of mRNA to tRNA 3 genes/1 codon at a time to put together proteins by stringing amino acids together (happens in ribosomes)
200

Why can't heritability be used to explain how much a particular trait is the result of genes or environment within an individual?

There is no way to isolate genes and environment within a single person. This is why we use twin studies, adoption studies, and animal studies to control for either environment or genetics and identify patterns among a population. 

200

What is the correct way to write scientific name for a cockatoo: cacatua goffini

Cacatua goffini or Cacatua goffini

genus capitalized, species not capitalized; both underlined or italicized

300

Why are some genes, such as freckles and red hair, more likely to be inherited together than genes for other traits?

  • violations of independent assortment: linkage - genes located close together on the chromosome are more likely to be inherited together

these closely placed genes are called “linked” because inheriting one means you’re more likely to inherit the other

300

DNA is used as a code to help cells build proteins, but not all genes are used for this purpose. What are the two categories of genes and what do the non-coding genes do?

  • some genes code for proteins (exons) and other genes regulate DNA activity (introns – not coded into mRNA). For example, an intron may “alert” an exon that it needs to start the process of transcription.  
  • Introns make up most of the human genome, but we don’t know why most of them exist
300

A pair of monozygotic twins are raised separately, but develop extremely similar personalities. How heritable (high/low) is personality and how do you know?

  • High heritability - heritability is the percent of variance that can be explained by genes rather than environment
  • monozygotic twins develop from the same gametes and are genetically identical
  • If the outcome is the same and the genes are the same, any variance must be attributed to the environment
300

Birds and butterflies both evolved to have functional wings allowing them to fly in response to pressures in their environments. Would this relationship be included in phylogeny? Why or why not?

  • homologous traits (similar by virtue of common descent) are the basis of phylogenies
  • analogous traits (similar by virtue of common environments) are not
  • Birds and butterflies can both fly to access food and escape predators, but they did not gain this trait from a common ancestor
400

If a mother and father are both carriers for a disease, what are the chances their child will express the disease? How do you know?

  • Carrier - Has the “bad” allele, but it is not present in their phenotype
  • Punnet square - 25% chance to express
400

How can a person's environment alter their traits without necessarily changing their DNA?

  • Epigenetics – Study of factors that turn genes on and off. Some of these factors can result in changes that do not involve changes to the DNA itself but can be inherited. 
  • DNA wound around histones making some sections resistant to transcription at any given time
400

Jenna always thought she was very different from her parents because she loved to be outside while they never set foot outdoors unless they had to. Recently, she found out that she was adopted and that her biological mother was a botanist studying flowers in Japan. What does this situation tell us about the heritability of the trait for wanting to be outside?

  • This trait is more similar to the biological parents rather than the adoptive parents
  • this trait is more due to genes inherited from the biological parent than environment created by the adoptive parents - highly heritable
  • Adoption studies allow us to separate genetic and environmental influences to study heritability
400
What does it mean if species are close together on a phylogenetic tree? Give an example.

The closer they are, the more recent their common ancestor

Sea lions and seals are connected on a phylogenetic tree and share a very recent common ancestor. 

Sea lions also share a common ancestor with dogs, but it is farther back in their history so the branch of the tree splits sooner.

500

Explain why a male is more likely to express the x-linked recessive trait for color blindness than a female. 

  • gene for disorder is on the X chromosome, 2 in females, 1 in males
  • Males only have one X, if it has recessive allele then it will be expressed
  • Females must be homozygous for recessive allele to be expressed
500

Jason has been diagnosed with sickle cell and is very upset. He asks his doctor why this happened and what he could have done to prevent it. How would you answer his questions?

  • types of mutations: point mutations, insertions, deletions, frame shifts
  • sickle cell is caused by a point mutation - T is replaced with A causing the codon to code for the incorrect amino acid
  • nothing Jason could have done to prevent this genetic mutation
500

The average variance from an experimental environment is known to be VE=350. Given a group of heterogenous mice with a total variance of 685, how would you determine the heritability of the trait being studied?

  • Genetic variance=Total variance-Environmental variance
  • Heritability=Genetic variance/total variance
  • Heritability = (685-350)/685
  • must be expressed as the percent variance attributable to genes
500

Darwin's theory of evolution by natural selection was inspired by the different beak shapes he observed among the finches of the Galapagos islands. How and why did these different beak shapes develop?

  • Certain types of food were more abundant in different areas of the Galapagos
  • To survive, the birds needed to be able to access and consume the type of food available in their area
  • those birds whose beaks were especially suited to the food in their region were more likely to survive and pass on the genes for that beak type
  • those with ill-suited beak shapes ate less and were less likely to reproduce
  • food type was a selection pressure, natural selection favored beaks that could access certain foods, finches evolved different beaks depending on the food in their area