Genetics: DNA, RNA, and proteins Flashcards
Each chromosome is long, but the DNA is wrapped around proteins that make them
shorter
What is the key to distinguish between transcription and translation in gene expression?
DNA and RNA are both nucleotide, so they have the same language (transcription)
When you move from RNA to amino acids, you need to translate it
When DNA is transcribed into RNA, thymine is replaced into what base?
Uracil
Why do triplets of RNA code each amino acid rather than twins?
There are 21 amino acids in total. Twins would only result in 4^2 = 16 combinations. Triplets allow for expression of each amino acid.
What could a base pair switch mutation cause in terms of protein production?
A protein codon could turn into a stop codon. making an incomplete protein that doesn’t work
Only around __% of the DNA in our chromosomes codes for a gene
3
What are introns? (intragenetic region)
Parts of the DNA that are not part of mRNA.
What are exons? (expressed region)
Any part of the gene that will encode
Where does DNA to RNA transcription occur?
In the nucleus, as you’re not gonna take the chromosome out of it
Hemophilia is an _-linked _________ disorder
X, recessive
What is a sex-linked gene?
Any gene located on a sex chromosome
What affliction is a common human sex-linked disorder caused by a malfunction of light-sensitive cells in the eyes?
Red-green colourblindness
What false conclusion did the scientific community accept for 33 years?
That humans have 48 chromosomes. We now know that there are 46.
What is gene mapping?
Using methods to identify they locus of a gene and the distances between genes
What is a genetic map and what is a physical map?
Genetic maps are based on genetic linkage (recombination) information)
Physical maps use actual physical distances measured in DNA base pairs
What are gene maps used for?
Many reasons, including identifying a gene that is responsible fora particular trait or disease
Which chromosome is the CF gene found on? How was it found?
Chromosome 7
Scientists compared DNA sequences in normal persons and individuals with CF
What is nondisjunction? What are the 3 forms?
The failure of homologous chromosomes or sister chromatids to separate properly during cell division or meiosis, resulting in the wrong number of chromosomes in daughter cells/gametes
- Failure to separate a pair of homologous chromosomes in meiosis 1
- Failure to separate sister chromatids during meiosis 2
- Failure to separate sister chromatids during mitosus
What can nondisjunction cause in relation to reproduction?
A zygote would have an extra chromosome
What is down syndrome?
A condition in which an individual has an extra or part of an extra chromosome 21.
In down syndrome, where does the extra chromosome usually come from?
The mother
The incidence rate of down syndrome increases as the mother ____
ages
What 2 errors can happen during recombination?
Deletion or duplication of the genes that are to be crossed over
What causes Di George syndrome?
A meiotic deletion in chromosome 22
Give a brief summary on the discovery of the structure of DNA (4 events)
- 1900s Kossel found the 4 bases
- 1920s Levene determine that DNA is made of a string of nucleotides linked together in a chain
- 1950 Chargaff found the proportions of the bases (A=T, C=G)
- 1950s Watson+Crick examined X-ray image of DNA and proposed double helix model
In the DNA double helix, the outside of the helix is made of the ______ ________ compounds and the rungs are made of the _________ _______. In addition, the strands go from 5’ to 3’ on one and __ to __ on the other
sugar-phosphate, nitrogenous bases, 3’, 5’
How does DNA replication actually occur?
DNA unwinds by unzipping the base pairs. Then, new complementary strands are created on each split by DNA polymerase, resulting in 2 identical double helix stands
What is gene expression? Describe the 4 steps
The conversion of DNA into a protein
- DNA is transcribed into RNA by RNA polymerase
- RNA is modified into mRNA and leaves the nucleus
- mRNA is translated into an amino acid chain
- The amino acid chain is folded into a protein
What is an RNA triplet codon?
A series of 3 bases that translates into an amino acid.
What is the purpose of the start and stop codon in mRNA?
It determines the start and end of a gene coding sequence
How can each gene make more that one protein?
mRNA can be spliced in various ways to remove different regions (removing some exons and all introns)
Where are proteins made?
On ribosomes located in the cytoplasm or attached to the rough endoplasmic reticulum
How does mRNA and ribosomes make proteins?
- mRNA attaches to ribosomes
- Ribosome moves along the mRNA, reading the codons
- As it moves, different tRNA molecules that have amino acids on one end and anti-codons on the other that match up with the base pairs attach to the mRNA
- The polypeptide chains grows until the stop codon is reached
The cell can regulate which genes are ________ by controlling the flow of information in gene expression
expressed
What is gene regulation?
How a cell controls which genes are turned on and which genes are silenced
Genes can be turned on or off based on _________________ signals
environmental
How do transcription factors and promoters regulate gene expression?
DNA promoters are short regions of DNA upstream of the gene they regulate
Transcription factors are proteins that bind to the promoters. This binding initiates RNA transcription from the gene
