Genetics Flashcards
The units of inheritance
Genes
Diseases caused by a mutation in a single gene
Mendelian
XY code a
Man
XX code a
Female
Cystic fibrosis is an example of a
Mendelian Disease
The central dogma of molecular biology
DNA>RNA>Protein
The study of sets of genes in one or more species
Genomics
On average 50% of children are affected with the disease and 50% are unaffected
Autosomal Dominant
On average 25% of children are normal, 50% are carriers and 25% are affected with the disease
Autosomal Recessive
On average 50% of male children from a carrier female will have the disease & 50% of female children will be carriers
X-linked
Huntington’s disease is an example of
Autosomal Dominant
What type of mendelian disorder is cystic fybrosis?
Autosomal recessive
Haemophilia is an example of
X-linked recessive
What diseases are treated by by suppression of
expression of the mutant gene?
Dominant diseases
What diseases are treated by introducing a normal copy of the gene?
Recessive diseases
Two genes that occupy the same position on
homologous chromosomes.
Allele
The entire set of genes in an organism.
Genome
A fixed location on a strand of DNA where a gene or one of its alleles is located.
Locus
Having identical genes (one from each parent) for a particular characteristic.
Homozygous
Having two different genes for a particular characteristic.
Heterozygous
The allele of a gene that masks or suppresses the expression of an alternate allele
Dominant
An allele that is masked by a dominant allele
Recessive
The physical appearance of an organism
Phenotype
A genetic cross involving a single pair of genes
Monohybrid Cross
Predicted that genes occur in pairs
Mendel
Mendel’s Principles
- Principle of Dominance
- Principle of Segregation
- Law of dominance
Mendel’s Law of Dominance
One factor in a pair of traits dominates the other in inheritance unless both factors in the pair are recessive.
An organism with two identical alleles for a character
Homozygote
An organism with two different alleles for a gene
Heterozygote
Matings that involve parents that differ in two genes
Dihybrid Cross
The tendency of genes from the same chromosome to remain together when they enter the gamete.
Linkage
The appearance of new combinations of alleles.
Recombination
____ dominance occurs when phenotypes of the heterozygote and dominant homozygote are identical.
Complete
____ dominance, the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties.
Incomplete
____ dominance, two dominant alleles affect the phenotype in separate, distinguishable ways.
Co
Pleiotropy
The concept that most genes have multiple phenotype effects.
Cell division involving somatic cells
Mitosis
Cell division involving gametes
Meiosis
One pair of homologous chromosomes
A diploid cell
Each cell receives only one of the homologues
(Half a chromosome)
Meiosis I
Each cell receives only one sister chromatid
Meiosis II
9:3:3:1 inheritance pattern
Dihybrid Cross
How many chromosomes are there?
23
Thomas Hunt Morgan worked with
Drosophila flies
Offspring with a phenotype matching one of the parental (P) phenotypes are called
Parental Type
Offspring with nonparental phenotypes are called
Recombinants
A protein structure that forms between homologous
chromosomes (two pairs of sister chromatids) during meiosis
The synaptonemal complex
The farther apart two genes are, the ____ the probability that a crossover will occur between them
higher
Griffith’s Experiment
Insert different forms of strep into mice
Demonstrated bacterial transformation
The movement of genetic material between unicellular and/or multicellular organisms other than by the vertical transmission of DNA from reproduction.
Horizontal Gene Transfer
The uptake of short fragments of naked DNA by naturally transformable bacteria.
Transformation
The transfer of DNA from one bacterium into another via bacteriophages.
Transduction
The transfer of DNA via sexual pilus and requires cell-to-cell contact.
Conjugation
A polymer of nucleotides, each consisting of a nitrogenous base, a sugar, and a phosphate group
DNA
The nitrogenous bases of DNA
- Adenine,
- Thymine,
- Guanine,
- Cytosine
- The base composition of DNA varies between species
- In any species the number of A and T bases is equal and the number of G and C bases is equal
Chargaff’s Rules
To pack chromatin, DNA are wrapped around
Histones
Euchromatin
Loosely packed chromatin
Heterochromatin
Densely packed chromatin
Required properties of DNA
- It must contain the Information required to construct and maintain life forms
- Must be Inherited Intact through Generations
- It must be Replicated with High Precision
A nucleotide is made up of
Phosphate + Sugar + Base
Purines
- Adenine
- Guanine
Pyrimidines
- Thymine
- Cytosine
- Uracil (RNA)
- dAMP
- dGMP
- dCMP
- dTMP
The 4 types of nucleotides
The only linkage allowed between nucleotides
Phosphodiester bond
The directionality of DNA is
5’ to 3’
Replication of DNA is
semi-conservative
DNA synthesis occurs via
primer extension
DNA polymerase can only add nucleotides to the ____ end of a replicating strand.
3’
The ____ strand copies continuously in the direction of unwinding
Leading
The ____ strand copies in segments
Lagging
Through Okazaki Fragments
Okazaki fragments are joined by
Ligase
Uracil replaces ____ in RNA
Thymine
- This is the RNA transcribed from ‘protein-coding’ genes
- encode the information for specific proteins
mRNA
- Is a structural & functional component of Ribosomes
- is very stable
- is a non-coding RNA
rRNA
- Very abundant and very stable
- A non-coding RNA
- ‘Clover-leaf’ secondary structure
tRNA
The synthesis of RNA based on a DNA template
Transcription
DNA sequences that guide RNAP to the beginning of a gene to start transcription
Promoters
DNA sequences that specify the termination of RNA synthesis, and the release of RNAP from the DNA
Terminators
Roles of RNAP
RNA Polymerase
- Initiates transcription
- Elongates the mRNA chain
- Terminates transcription
The process of making an mRNA copy of the DNA sequence via RNAP
Elongation
RNAP I - makes
rRNA
RNAP II - makes
mRNA
RNAP III - makes
tRNA
____ remove introns from pre-mRNA
Spliceosomes
Gene regulation dictates
- When
- Where
- How much
The fundamental unit of gene organization and regulation of gene expression in Prokaryotes
Operons
A set of genes encoding enzymes each of which is required in the same metabolic pathway
Operons
Genes that encode Regulatory Proteins that control the expression of other genes
Regulatory Genes
That may function either as Repressors
(or Activators) of gene expression
Regulatory Proteins
DNA + Histones =
Nucleosome
- Chromatin is compacted
- Histone tails have methyl groups
- DNA is inaccessible
Heterochromatin
- Chromatin is ‘open’ or ‘loose’
- Histone tails have acetyl groups
- DNA is accessible
Euchromatin
Amino acids linked together via peptide bonds
Polypeptide
A polymer with a sequence of 20 different amino acids
Protein
The mRNA sequence is decoded _ bases at a time
3
A codon
One codon specifies ____ amino acid
one
The decoding machinery disengages from the mRNA when it encounters a
STOP Codon
The Anticodon region recognizes and binds to a codon in _RNA by base pairing
m
How does a given tRNA acquire its specific amino acid?
Aminoacylation
What do ribosomes do?
Make protein
When a ____ enters the A site of the ribosome, a protein called Release Factor is recruited
STOP codon
- many ribosomes translating a single mRNA
- A protein production line
Polysomes
Individuals with different forms (alleles) of the same gene
Variants
Variants are typically referred to as ____, if they have
been deliberately produced in the laboratory
mutants
Somatic mutations
Not inherited
Germline mutations
Inherited
What is a mutation caused by external factors?
Induced
What is a mutation caused by errors in DNA replication?
Spontaneous
Chemical mutagens that cause cancers.
Carcinogens
Example of a missense mutation
Sickle Cell Disease
