Genetics Flashcards
What are the 3 primary functions of genetic material?
- Coding for products
- Passing info between cells
- Passing info to the next generation
What are two factors that determine what an organism is like?
- Gene sequence
2. The regulation of the expression of those genes
What is the genome?
The complete sequence of nucleotides of the genetic material
Is the genome usually DNA or RNA?
DNA, but RNA for certain viruses
Greek: epi?
Around
What are changes in the products and their amounts from the same gene code due to?
Different responses to the cellular environment
What are epigenetics?
Changes that are made around the genome that do not alter the nucleotide sequence; they simply instruct the cellular machinery how to read the genome
What are 3 examples of epigenetics?
- Attachment of chemical markers to the genome
- Histone protein modification
- Use of non-coding RNAs
What kind of epigenetics can be passed on to the next generation?
- Attachment of chemical markers to the genome
2. Histone protein modification
What is the MCAT definition of a gene?
Nucleotide sequence that can code for
- A certain product/set of products depending on factors like alternative splicing and protein modification
- A trait (genetically influenced characteristic
What is the Central Dogma of gene expression?
DNA is transcribed to RNA, which is translated to amino acids to form a protein
Who uses the Central Dogma of gene expression? Who does not?
All living organisms
Retroviruses
How are double stranded DNA sequences arranged in eukaryotic cells?
Chromosomes
What are histones? What kind of DNA is wrapped around them?
Globular proteins around which sections of DNA that are not in use are wrapped tightly
What makes the DNA wrap around histones?
The net positive charge of histones attracts negatively charged DNA strands
What is a nucleosome?
8 histones wrapped in DNA
What are solenoids?
Wrapped nucleosomes
What are supercoils?
Wrapped solenoids
What is chromatin?
All the nucleosomes = The entire DNA/protein complex (w/ very small amount of RNA)
How is the mass of chromatin divided?
1/3 DNA
2/3 protein
Small amount of RNA
Where does chromatin get its name?
The large amount of basic amino acids in chromatin allow is to absorb basic dyes
What about chromatin influences gene expression?
Its structure; how compact/coiled it is
What is heterochromatin?
Chromatin that is tightly condensed
What is constitutive heterochromatin?
Permanently coiled heterochromatin
What is eurochromatin?
Chromatin that is uncoiled and allows for transcription
When is eurochromatin coiled?
During nuclear division
What is single copy DNA? What does it do?
Nucleotide sequences represented by only one copy of a nucleotide sequence and are associated with regions of eurochromatin that are being actively transcribed
It codes for proteins
What is repetitive DNA? What does it do?
Multiple identical consecutive nucleotide sequences
It does not code for proteins
Where is DNA found in animals?
In the nucleus and mitochondria
What is the most common example of epigenetic regulation through chemical change?
DNA methylation
What is DNA methylation?
Addition of an extra methyl group to particular cytosine nucleotides
What is the effect of DNA methylation?
Winds DNA more tightly
What is non-coding RNA (ncRNA)? What does it contribute to?
Sections of RNA that do not code for proteins and contribute to the regulation of chemical changes that affect chromatin structure
What is a somatic cell?
Any cell of a living organism other than the reproductive cells
How many DNA molecules in the nucleus of somatic cells?
46
What are homologues?
Two chromosomes that code for the same traits
How many homologous chromosomes do humans have?
23
What is a trait vs a version of the trait?
Eyes vs blue/brown…
What are alleles?
Different versions of the same gene
What are diploid cells?
Cells that contain homologous versions of chromosomes
What are haploid cells?
Cells that do not contain homologous versions of chromosomes
What is a methyl group?
R-CH3
Can genetic information code for non-protein products? Like?
Yes; RNA
Can you say that genetic differences between living organisms are negligible?
No; they are small but not negligible
When are chromosomes formed? From what?
During cellular division from chromatin that is more condensed
Does the number of chromosomes in a human cell double during replication?
No
What are chromatids?
The two strands of chromosomes joined together by a single centromere, formed from the duplication of the chromosomes during the early stages of cell division
What is G0?
The non-growing phase of a cell’s life cycle
When does most protein production take place?
During G0
What are the 4 types of RNA
- Ribosomal RNA (rRNA)
- Transcription RNA (tRNA)
- Messenger RNA (mRNA)
- Small nuclear RNA (snRNA)
What does DNA become to produce proteins?
DNA –> mRNA –> proteins
What would happen if DNA was directly translated into amino acids?
Every cell in an organism would be the same
What are the 3 main stages of transcription?
- Initiation
- Elongation
- Termination
What are transcription factors?
DNA binding proteins that identify the promoter on the DNA strand
What is a promoter on the DNA strand?
Sequence of DNA nucleotides that designate a beginning point for transcription
What happens during transcription initiation? 2 stages
- Transcription factors bind to the DNA at a promoter and assemble into a transcription initiation complex which includes RNA polymerase
- RNA polymerase unzips the DNA creating a transcription bubble
What is RNA polymerase?
The major transcription enzyme
What is the consensus sequence?
The most commonly found promoter by a given species of RNA polymerase
What does variation of the consensus sequence cause?
RNA polymerase will bind less tightly and less often to the promoter which means the genes will be transcribed less frequently
What happens during transcription elongation?
RNA polymerase transcribes only one strand of DNA into one complimentary RNA nucleotide sequence
What is the template strand?
The transcribed DNA strand
What is another name for the template strand?
Antisense strand
What is the coding strand? What does it do during transcription?
The strand of DNA that is not being transcribed by RNA polymerase; it protects its partner from degradation
What is another name for the coding strand?
Sense strand
In what direction does RNA polymerase move along the DNA strand?
3’ –> 5’
In what direction is the RNA strand being built by RNA polymerase?
5’ –> 3’
Are errors in transcription passed on to the next generation?
No
Are transcription errors harmful?
Usually not