Lecture 2

How many autosomes are in a human cell?

• 22 (two copies of each) = 44

What do you call the region between the +1 site for transcription and the start codon?

• The 5’ UTR

What is the difference between an exon and an intron?

• Exon is included in RNA transcript and intron is spliced out

Is the 5’UTR part of an exon or an intron?

• part of the first exon

What is added when a transcript is processed?

• The polyA tail and 5’ cap

Where does translation start?

• at the start codon on the mRNA

What is the open reading frame?

• protein-coding sequences

• everything that gets translated

What percent of the human genome is part of an open reading frame?

• 3%

Are there more protein coding genes or non-protein coding genes?

• Non-protein coding

What is the most common type of retrotransposon in the human genome?

• ALU - type of SINE

What strategy does the genome have to try to prevent retro transposons from disrupting it?

• human genome is primarily in a suppressive state

Why does a pseudogene of a protein coding gene present an opportunity for evolution to make a new gene with a different function?

• pseudogene - highly resembles functional gene but doesn’t encode for the protein

• new copy can evolve into something new that is funcitonal

  • not making any necessary proteins

What are two (big) parts of human chromosomes that are made of repetitive elements?

• telomeres

• satellite DNA at centromeres

What is an acrocentric chromosome and what can be found on these in the human genome?

• Chromosome where the P-arm is very short

• P-arms hold tandem arrays of ribosomal RNA genes

  • repetitive sequence

Why is it necessary to have a unique repetitive element at the ends of chromosomes?

• proteins that bind the repetitive telomere sequences to make a cap to prevent chromosomes from sticking to other chromosomes

• telomerase binds the repeat to prime replication at the end of the chromosome

Polymorphisms:

What are the major differences between types of polymorphisms in the human genome?

• size of polymorphism

• whether a repeating unit involved is involved or not

• whenever DNA was arranged or not

What are three practical uses for polymorphisms in the human genome?

• linkage analysis

• DNA fingerprinting

  • different for each person

• genome-wide association studies

Linkage analysis and pedigrees:

What is the difference between phenocopy and genetic heterogeneity?

• phenocopy - same phenotype of a different genetic cause

• genetic heterogeneity - same mutation with a range of phenotypes

Why do phenocopy and genetic heterogeneity disrupt linkage analysis?

• linking a region of the genome to a mendelian trait, if there are two genes mutant in the system, the trait will not be mapped to a single locus

How are ascertainment bias and anticipation similar?

• if we know a history of a mutation with anticipation, we are likely to diagnose earlier?

• result in the studied trait or disease being detected at younger ages in subsequent generations of a family

What is a TAD?

• topologically associated domain

• self-interacting genomic region, DNA sequences within a TAD interact physically with each other more frequently than with sequences outside TAD

How do TADs form?

• boundary elements bound by CTCF protein define TAD

• the DNA of the TAD loops out creating a physically separate compartment for genes within TAD