Genetics Flashcards
Specific sequence allowing an initial binding site for RNA polymerases
Promoter region
What structure opens up the DNA strands during Transcription?
RNA Polymerase
What acts as a “switch” to initiate transcription?
Phosphorylation
These are proteins involved in the process of transcribing DNA into RNA, by initiating and regulating the transcription of genes
Transcription factors
Which stages of the cell cycle do chemotherapy drugs mainly target?
“S” and “M” phases
What are the three main components to DNA structure?
The nitrogenous bases (adenine, thymine, guanine, and cytosine), a phosphate group, and a 5-carbon sugar group
What is the difference between chromatin and chromosomes?
Chromatin fibers are long and thin. They are uncoiled structures found inside the nucleus. Chromatin has a lower order of DNA organisation.
Chromosomes are compact, thick and ribbon-like. Chromosomes have a higher order of DNA organization.
What is chromatin?
DNA is packaged by special proteins called histones to form chromatin. The chromatin further condenses to form chromosomes.
How can mutations affecting DNA packaging cause disease?
Mutations affecting DNA packaging are often fatal, but Rubinstein-Taybi syndrome is one example.
What disease results from a mutation in histone acetyl-tranferase CREBBP?
Rubinstein-Taybi syndrome, which features mental retardation, facial abnormalities, broad thumbs, and broad great toes.
The study of heredity, the process by which characteristics are passed from parents to offspring
Genetics
A unit of biological information that encodes a specific protein or regulatory molecule
Gene
The most common variations that we find within genomes are known as
single nucleotide polymorphisms (SNPs)
What are the four different nitrogenous bases in DNA?
Adenine, Thymine, Guanine, and Cytosine
Which nitrogenous bases are the purines?
Adenine and Guanine
Which nitrogenous bases are the pyrimidines?
Cytosine and Thymine
Adenine pairs with _________ in DNA
Thymine (remember “apples in trees”)
Cytosine pairs with __________
Guanine (remember “cars in the garage”)
How many pairs of homologous chromosomes do human cells have? (And the one exception to that?)
23 pairs (exception is gametes with 23 chromosomes)
Genetic material is duplicated in which stage of the cell cycle?
The “S” stage (S for Synthesis)
How many pairs of chromosomes are there at the end of S phase?
46 pairs (92 chromatids)
Which stage of mitosis is this?
- Chromatin begins condensing into chromosomes
- Mitotis spindles begin to form
- Centrosomes begin to move in opposite directions
- Nucleolus dissapears
Prophase
Which stage of mitosis is this?
- Chromosomes align on a theoretical line known as the metaphase plate
- Centrosomes have moved to opposite ends of the cell
- Cell checks that all chromosomes are aligned properly along the metaphase plate
Metaphase
Which stage of mitosis is this?
- Sister chromatids are pulled to opposite ends of the cell
- The spindle fibres contract, breaking the chromatids at the centromere and moving them to opposite poles of the cell
- Spindle fibres not attached to chromatids will elongate the cell to prepare the cell for division
Anaphase
Which stage of mitosis is this?
- The cell has elongated and is nearly finished dividing
- Cell-like features begin to reappear such as reformation of two nuclei (one for each cell)
- The chromosomes decondense and unwind into chromatin
- Mitotic spindle fibres are broken down
Telophase
This is the process where a single cell divides twice to produce four cells containing half the original amount of genetic information, resulting in four genetically unique gametes.
Meiosis
Name the three key elements of Meosis I
- DNA replication
- Recombination
- Cell division
Which phase of meiosis involves a further cell division cycle?
Meiosis II
Interphase consists of which steps? (hint: cell cycle)
G1 - Metabolic changes prepare the cell for division. Cell contents (excluding the chromosomes) are duplicated
S phase- Genetic material is replicated. Each chromosome now consists of two identical sister chromatids
G2- The cell “double checks” the duplicated chromosomes, making repairs as needed. Metabolic changes assemble the cytoplasmic materials necessary for mitosis and cytokinesis.
Which phase of meiosis is this?
- Each chromosome is now composed of two sister chromatids containing identical genetic information.
- The chromosomes pair up so that both copies of Ch 1 are together, then Ch 2, and so on.
- RECOMBINATION/CROSSING OVER OCCURS HERE
Prophase I
Which phase of meiosis is this?
- The chromosomes line up next to each other along the equator of the cell.
- Meiotic spindle fibres attach to one chromosome of each pair
Metaphase I
Which phase of meiosis is this?
- The pair of chromosomes are pulled apart by the meiotic spindle, which pulls each chromosome to opposite poles of the cell.
- In this stage, the sister chromatids stay together
Anaphase I
Which phase of meiosis is this?
At each pole of the cell, a full set of chromosomes gather together.
- The single cell then pinches in the middle to form two separate daughter cells, each containing a full set of chromosomes within a nucleus
Telophase I
Which phase of meiosis is this?
Chromosomes condense into X-shaped structures
- The membrane around the nucleus dissolves away, releasing the chromosomes
- Centrioles duplicate and meiotic spindle re-forms
Prophase II
Which phase of meiosis is this?
- The sister chromatids line up end-to-end along the equator of the cell
- Centrioles are now at opposite poles
- Meiotic spindle fibres at each pole attach to each of the sister chromatids
Metaphase II
Which phase of meiosis is this?
- Sister chromatids are then pulled apart and move to opposite poles
- The separated chromatids are now individual chromosomes
Anaphase II
Which phase of meiosis is this?
- The chromosomes complete their move to opposite poles of the cell.
- The full set of chromosomes gather together at each pole
- The cells go through cytokinesis to form four haploid (genetically unique) “granddaughter” cells, or gametes
Telophase II and cytokinesis
This is the exchange of genetic material between two strands of DNA that contain long stretches of similar base sequences
Homologous recombination
This process plays a critical role in the repair of double stranded DNA nicks and increases genetic diversity by enabling the shuffling of genetic material during chromosomal crossover in meiosis.
Homologous recombination
This is a type of trait determined by the expression of a SINGLE gene or allele
Monogenic trait
Which type of trait follows Mendel’s law of heredity?
Monogenic traits
This is when disease would result from a single pair off genes is involved
Monogenic disease
List some examples of monogenic diseases
Sickle cell anemia
Cystic fibrosis
Huntington’s disease
Duchenne’s muscular dystrophy
This terms refers to a characteristic that is controlled by more than two genes- also called “multifactorial inheritance.”
Polygenic traits
This type of inheritance patterns normally show a normal (bell-shaped) distribution curve. It shows continuous variation, such as the variations of skin pigmentation.
Polygenic traits
Name some examples of diseases with polygenic traits
Hypertension
Coronary artery disease
Diabetes mellitus
Name some examples of X-linked conditions
Haemophilia
Duchenne’s muscular dystrophy
Genetic conditions associated with mutations in genes on the X chromosome are called
X-linked disorders
How do men develop an X-linked genetic condition?
In males (who only have one X chromosome), a mutation in the copy of the gene on the single X chromosome causes the condition, so they would have inherited the mutated gene from their mother.
Describe how a female would express an X-linked condition
Females (who have two X chromosomes) must have a mutation on both X chromosomes in order to be affected with the condition.
Describe how a daughter could be a carrier of an X-linked condition, but not express the disease
If only the father or the mother has the mutated X-linked gene, the daughters are usually not affected and are called carriers because one of their X chromosomes has the mutation but the other one is normal.
What type of genetic mutation is responsible for sickle cell anemia? (hint: N-S…)
Non-synonymous changes
Mutations in which genes result in maternally inherited diseases (other than X-linked)?
Mitochondrial genes
Leber’s hereditary optic atrophy and myoclonic epilepsy with ragged red fibres are what type of genetically inherited disorders?
Mitochondrial disorders
DNA mutations in the germline result in ________ changes.
heritable
When DNA damage/mutations occur in the _______, this results in changes that are only present within the individual’s lifetime. Contribute to ageing and diseases such as cancer
soma
Can a mutation within soma cells get passed on to pregency cells?
Yes, the mutation will carry on into the progeny cells of any reproduction /replication from the original mutated cell.
What is the source of all genetic variation?
Mutations
Genetics mutations can be harmful, neutral, or _________.
advantagous
Most mutations are slightly ___________
deleterious
Polymerases invloved in DNA replication have a _________ exonuclease activity, this allows for proof reading.
3’ to 5’
There are greater than 130 specific genes invloved in DNA repair. Name the three types of genes mentioned in lecture that perform DNA repair
- _______ excision repair
- _______ excision repair
- _________ repair
- Base
- Nucleotide
- Mismatch
What type of damage can occur as a result of radiation exposure?
Double stranded breaks in DNA
There is a specific system of repairing double stranded DNA breaks, often the result of radiation exposure. What is this system called?
Recombination repair
Name an example of a disease resulting from a mutation in components of the UV repair pathway (these patients are unable to remove thymine dimers)
Xeroderma pigmentosum
This is a group of inherited genetic disorders resulting from recombination errors in meiosis. Results in peripheral nerve damage.
Charcot-Marie-Tooth disease
Non-dysjunction in meiosis results in what type of genetic disorders? (2)
Trisomies and monosomies
What are the trisomy disorders that are non-fatal?
Trisomy 13 = Patau’s
Trisomy 18 = Edward’s
Trisomy 21 = Down’s
And sex chromosome trisomies such as “Triple X syndrome”
Mutations in which repair genes are the leading contributor to genetic pre-disposition to colorectal cancer?
Mismatch repair genes
Name the RNA nucleotides in their respective base pairs:
Adenine with _____
Guanine with _____
Uracil, cytosine
This is a specific sequence allowing an intial binding site for RNA polymerase (like a TATA box)
promotor region
Which enzyme separates the two strands of the DNA double helix prior to transcription?
DNA helicase
The DNA molecule unwinds and separates in a process known as
melting.
What attaches to the DNA binding site before RNA Polymerase initiates unwinding of the DNA strands?
Transcription factors
Which enzyme (mainly) initiates transcription?
RNA polymerase
RNA polymerase READS the DNA in a ________ direction, and then SYNTHESIZES the new mRNA strand in the _______ direction.
Reads- 3’ to 5’
Synthesizes mRNA- 5’ to 3’
The new mRNA molecule continues to be synthesized in the 5’ to 3’ direction until a ______ sequence is encountered.
stop
RNA strands have the nucleotide ________ in place of thyamine.
Uracil
Which strand of DNA carries the genetic information?
The coding strand
RNA polymerase attaches to which strand of the DNA to begin synthesizing mRNA?
the template strand
Out of the three different types of RNA polymerase, which is the type that makes proteins?
RNA Polymerase II
What acts as a “switch” to initiate transcription?
Phosphorylation
What does RNA polymerase require at the promotor region in order to bind to the DNA?
Transcription factors
An immature strand of mRNA (aka “pre-mRNA”) has introns and exons. Which of these codes for proteins?
Exons
Mneumonic for remembering exons vs introns?
“EXons are EXpressed,” and
“INTRons are IN the TRash”
Post-transcriptional splicing is performed by a complex known as a
spliceosome
The string of exons joined together after post-transcriptional splicing is called
mature RNA
Name one disease that was mentioned in lecture that can result from a splicing mutation
Cystic fibrosis (results from the skipping of an exon)
This is the process of creating proteins from an mRNA template
Translation
What reads mRNA in order to create a protein?
Transfer (t) RNA
These are molecular “bridges” that connect mRNA codons to the amino acids they encode
tRNA
One end of each tRNA has a sequence of three nucleotides called an _________ which can bind to specific mRNA codons.
Anti-codon
There are many different types of tRNA’s. Each type reads one or a few codons and brings the right _______ ______ matching those codons.
amino acid
Name the three stages of translation:
- Initiation
- Elongation
- Termination
A certain complex is needed in order to begin translation, where the ribosome assembles around the mRNA to be read, along with the first tRNA. This is known as the
Initiation complex
Name the three tRNA sites in the large ribosomal subunit
A site
P site
E site
What happens at the tRNA “A site?”
This is where a tRNA that is bound to an amino acid attaches to the ribosome. (Or think of it as “A for Accepts” an incoming tRNA
What happens at the tRNA “P site?”
P is the “peptidyl site,” where the polypeptide forms
What happens at the tRNA “E site?”
E is the “exit site,” where the tRNA that has already deposited its amino acid is EJECTED.
Which part of the ribosome (of the two subunits) has the translation initiation factors bound to it?
The small ribosomal subunit
This is the stage of translation where the amino acid gets longer. The mRNA is read one codon at a time, and the amino acid matching each codons added to a growing peptide chain.
Elongation
Once a new tRNA binds to the A site, what type of bond is formed between the two amino acids?
Polypeptide bond
Termination of translation happens when a _______ codon enters the ___ site.
stop, A
What are strings of amino acids called?
Peptides
What are proteins made of?
Strings of multiple peptides
Recognise the different levels of control of gene expression:
1. _____________ control affects the stage where DNA is turned into an RNA transcript
Transcriptional
Recognise the different levels of control of gene expression:
2. ___ processing control, such as splicing, affects the stage between RNA transcription and the production of mRNA
RNA
Recognise the different levels of control of gene expression:
3. This stage of gene expression affects the transport of the mRNA from the nucleus into the _________
cytosol
Recognise the different levels of control of gene expression:
4. mRNA _________ control takes mRNA and makes it inactive.
degredation
Recognise the different levels of control of gene expression:
5. ___________ control prevents the mRNA from being converted into a protein.
Translation
Recognise the different levels of control of gene expression:
6. “Protein acivity control” refers to the ability of a protein to either be active or ________.
inactive
Cystic fibrosis results from a defect in which gene, resulting in a non-functional protein?
CFTR
The most commonly mutated gene in people with cancer is
p53 (or tp53)
More than 50% of cancers involve a missing or damaged ______ gene.
p53
These are non-coding RNA’s that play a critical role in the regulation of gene expression
micro RNA’s
Roughly 50% of micro RNA’s are processed from _______, the remaining are from their own genes
introns
This type of RNA causes transcriptional REPRESSION by binding to or degrading mRNA targets
micro RNA
Dysregulation of ________ have been shown to affect the hallmarks of cancer, including
- sustaining proliferative signalling
- evading growth supressors
- resisting cell death
- activating invasion and metastasis
- inducing angiogenesis
micro RNA
In what types of cells are micro RNA’s heavily dysregulated?
Cancer cells
Name the two specific micro mRNA genes mentioned in lecture that, when deleted, play a role in cancer (specifically lung cancers and B-cell CLL)
miR-143 and miR-145
What is the function of the miR-143 and miR-145 genes, and how do they relate to cancer?
These genes act as tumour supressors to induce apoptosis. If these genes are deleted, the body cannot destroy cancerous cells, so they keep multiplying.
Protein structure is classified into four levels:
- Primary structure: the linear sequence of amino acids
- Seconday structure: Local folding
- Tertiary structure: 3D structure of the folded protein
- Quaternary structure: Multiple complexes of polypeptide chains
This is the linear sequence of amino acids that makes up the polypeptide chain
The primary structure of a protein
The primary amino acid sequence determines the final ________ structure of the protein.
tertiary
The beginning of the primary structure is called the ______ terminus, while the end of the structure contains the _______ terminus.
amino, carboxyl
This level of protein structure is where proteins are locally FOLDED into a variety of unique conformations ranging from long strand-like structures, turns in the chain, and helices.
Secondary
Name the three types of secondary structures
- alpha helix
- beta sheets
- beta turns
The “extended zigzag conformation of the polypeptide chain” is the
beta sheet
Anti-parallel beta sheets have hydrogen bonds between polypeptide chains that are
Linear
Parallel beta sheets have hydrogen bonds between polypeptide chains that form
at an angle
In the alpha helix conformation, the polypeptide backbone can wind up into a right handed helix, stabilised by ________ bonds via a Carboxyl group of one amino acid and an amide hydrogen 4 residues later.
hydrogen
An alpha helix forms readily becuase it makes optimal use of internal ________ bonds.
hydrogen
The inside of an alpha helix polypeptain chain is
hydrophobic
What part of the chemical structure on the outside of an alpha helix make it hydrophilic (towards the outside)?
the R groups
This connects the polypeptide chains between secondary structures such as alpha-helices and beta-sheets.
Beta turns
This brings about a 180 degree change in direction for the polypeptide chain.
Beta turn
Which amino acid is generally responsible for forming “kinks” in the polypeptide chain, producing a beta-turn?
Proline
This is the three dimesional structure of the folded protein
Tertiary structure
What produces the three dimensional structure (the tertiary structure) of a protein?
FOLDING
Myoglobin, Tumour Necrosis Factor alpha, and beta-barrels are examples of what level of protein structure?
Tertiary
This is the arrangement of multiple complexes of 3D polypeptide chains
Quarternary structure
Haemoglobin is an example of what level of protein structure?
Quarternary
List the main three factors (bonds, types of interactions) affecting protein folding
- Hydrogen bonds
- Ionic interactions/salt bridges
- Dispulphide bonds
This type of bond links amino acids in a polypeptide
Peptide bonds
Which type of bond has a partial double-bond character
Peptide bonds
This forms a weak electrostatic bond; interacts with slightly negative ions.
Hydrogen bonds
These are fairly strong electrostatic interactions between two formal charged side chains (one slightly positive, one slightly negative).
Salt bridges
This is a distance-dependent interaction between atoms or molecules that do not result from a chemical electronic bond. (Weak compared to ionic or covalent bonds)
Van Der Waals attractions
This is a special type of covalent interaction between the sulphur groups of cysteine. Very strong bond. Can happen on one peptide chain, or between peptide chains.
Dusulphide bonds
The strength of the interaction increases if a salt bridge forms within the more _______ interior of a protein.
hydrophobic
What is the main thing that drives folding and maintaining the overall structure of proteins?
The hydrophobic core
Proteins may fold into multiple __________.
domains
Protein domains can often be found in the primary sequence as sequence…
motifs
This is the term for a short stretch of residues (15 aa’s) that act as a postcode to send the protein to specific places within the cell
Signal sequence
This is the unfolding of proteins due to the breakage of non-covalent interactions and oxidation of disulphides.
Protein denaturation
Mutations in the DNA sequence can lead to a change in the ____ ________ sequence, which alters the tertiary structure of the protein.
amino acid
Substituting a glutamine for a valine results in what type of anemia?
Sickle cell anemia
Differences in the ___ group of the amino acid alter its chemical properties, such as charge
R
The molecules within an amino acid that have just a little bit of charge are called
polar
Non-covalent _____ chains can help stabilise protein structure.
side
What is the primary driving force in protein folding?
Hydrophobic interactions
In the nucleus, the DNA double helix is packaged by special proteins called ________ to form a complex called chromatin.
histones
