Lecture 2 - Genes, Chromosomes, and Genomes Flashcards Preview

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Flashcards in Lecture 2 - Genes, Chromosomes, and Genomes Deck (54)
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When are chromosomes in the pair linked condensed sister chromatid form?

After replication at metaphase during mitosis


What are the 6 eras of DNA discoveries?

1. DNA structure
2. Nucleosomes
3. Epigenome
4. Genome topography
5. Human genome project
6. ENCODE project


What was the goal of the ENCODE project? What did it accomplish?

Identify all regions of transcription, transcription factor association, chromatin structure, and histone modification in the human genome => 80% of it now has at least 1 biochemical function associated with it


What is the classic definition of a gene?

Portion of chromosome that determines a phenotype


What is the definition of a gene for our purposes?

DNA that encodes the primary sequence of some final gene product + the DNA that regulates the expression of that product (transcription initiation region, exons, transcription termination signals)


Central dogma of molecular bio?

DNA is transcribed into
RNA, which is translated into protein


What is a pseudogene?

Gene that has a mutation and whose expression has been turned off


How many base pairs in our genome?

3 billion


How many genes in human genome? How does this number change overtime?

About 25,000
Decreases with time


Describe mtDNA.

Circular double stranded DNA


How many chromosomes in every normal human somatic cell?

46 chromosomes


Why do we inherit mtDNA from our mother?

Because mitochondrial endonuclease G mediates breakdown of paternal DNA upon fertilization


What does delayed removal of paternal mitochondria cause?

Increased embryonic lethality, demonstrating that PME (Paternal Mitochondrial Elimination) is important for normal animal development


What are exons?

DNA coding segments


What is a hypothesis that explains why eukaryotes conserved introns?

Functional domain hypothesis: if you look at any protein and separate out the functional domains (binding site, allosteric sites) they are segregated on individual exons and can be mixed and matched to create a new protein, therefore the introns are there to increase diversity


What are the 4 types of transposons and what % of our DNA do they comprise?

1. Long interspersed elements (LINEs) - 21%
2. Short interspersed elements (SINEs) - 13%
3. Retroviruslike- 8%
4. Transposon remnants that differ greatly in length - less than 3%


What % of our DNA do introns and noncoding segments comprise?



What is an example of a retroviral DNA sequence with a specific and important biological function? When did this evolutionary adaptation occur and why?

Activation of salivary amylase in the human parotid gland is due to an LTR (long terminal repeat) enhancer that is part of a retroviral DNA sequence

The gene triplication of the amylase gene and its LTR enhancer to further enhance amylase secretion occurred after hominids split from chimpanzees. It may have provided selective advantage to the hominid lineage when they adopted a diet containing complex carbohydrates


What are the 2 types of miscellaneous DNA sequences?

1. Simple-sequence repeats (SSR)
2. Large segmental duplications (SD): segments that appear more than once in different locations


What is an example of a retrovirus that has an important function in embryology? Explain when it's expressed and what its function could be.

HERVK (human endogenous retrovirus type K) which is transcribed during normal human embryogenesis at the 8-cell stage and continuing through epiblast development preimplantation

Possible functions:
1. Protect from other viruses by occupying receptors
2. Express proteins to help implantation
3. Act as chaperones inside cells


What class of proteins is most rapidly adapting to our environment?

VIPs = viral interacting protein


What class of proteins is most rapidly adapting to our environment?

VIPs = viral interacting protein


What happens to a DNA sequence if there is no evolutionary pressure to maintain the sequence?

It is mutated


What is the mean gene size?

27,000 base pairs


Size of largest gene?

2.4 x 10^6 base pairs


Mean exon size?

145 base pairs


Number of pseudogenes?



What is the JCV1 3.0 cell?

"Minimal" cell with the lowest number of genes possible (473) to survive


What is the human genome project write?

10 year extension of the Human Genome Project, to synthesize the human genome


What can shorten telomeres?

1. Age
2. Smoking
3. Lack of exercise
4. Overweight