Genetics Flashcards
What is genetics ?
-The study of heredity in general and genes in particular
What is heredity ?
-The passing of traits from parent to offspring
Why did Mendel use pea plants?
-Easy to cultivate, available in many varieties, produce large number of offspring, strict control over mating/breeding
What is true breeding?
-When plants self-pollinate and all their offspring are of the same variety
What is hybridisation?
-Mating or crossing of two varieties
What is a monohybrid cross?
-A cross between two parents that breed true for different versions of a single trait
What did Mendel do?
-Cross pollinated two true breeding varieties studying one trait at a time, then recorded the inheritance of the chosen trait in the next generation, then allowed the F1 plants to self fertilise and observed F2
What is a homozygous gene?
-Gene possessing two identical alleles
What is a heterozygous gene ?
-Gene possessing two different alleles
What does Mendel’s law of independent assortment state?
-During gamete formation, different pairs of alleles segregate independently of one another
What is a genetic disease?
-A disease that is caused by an abnormality in an individuals DNA
What are the 4 types of genetic disorders?
-Single gene defects, chromosome abnormalities, multifactorial disorders, cancer
What is cancer?
-Progressive accumulation of mutations in different genes and different chromosomes abnormalities, usually in somatic cells
What are single gene disorders?
-Caused by changes or mutations that occur in the DNA sequence of a single gene, producing either an altered protein or no protein at all
What can single gene disorders lead to?
-Gain of function loss of function which result in a protein alteration or deficiency responsible for disease symptoms
What are the different mechanisms of inheritance?
-Autosomal dominant, autosomal recessive and X-linked recessive or dominant
What is an autosomal dominant mechanism?
-A single mutated allele is sufficient to cause the disease (heterozygous)
What is an autosomal recessive mechanism?
-Where both mutated alleles must be inherited to be affective (homozygous)
What is x-linked recessive or dominant?
-Mutated gene is present on the X chromosome
How do missense mutations alter coding in genes ?
-Base changes that alter the codon for an amino acid resulting in its replacement with a different amino acid
How do nonsense mutations alter coding in genes?
-Base changes that convert an amino acid codon to a stop codon resulting in premature termination of translation
What are silent mutations?
-Do not cause any change in an amino acid
What are frameshift mutations?
-Result from the insertion or deletion of one or more bases causing the alteration of the reading frame of the gene and a different set of codons leading to an altered ….
What can chromosome abnormalities be classified into ?
-Numerical and structural
What are numerical abnormalities ?
-When an individual is missing either a chromosome from a pair (monosomy) or has more than two chromosomes in a pair (trisomy)
What are structural abnormalities ?
-When the chromosomes structure is altered
What is euploid?
-Normal number of chromosomes
How is aneuploidy caused?
-Nondisjunction events in meiosis
What is mosaicism?
-The presence of two or more cell lines with different chromosome compositions in an individual
What can changes in chromosome structure cause?
-Deletions
-Duplications
-Inversions
-Translocations
What is a deletion ?
-Loss of a chromosome segment
What is a duplication?
-Repeats of a segment
What is inversion?
-Where a portion of the chromosomes has broken off, turned upside down and re-attached so genes occur in reverse order
What is a translocation mutation?
-A portion of one chromosome is transferred to another, can be reciprocal
What are multifactorial disorders?
-Diseases that show familiar clustering but do not conform to any recognised pattern of single gene inheritance
How are multifactorial disorders determined?
-The additive effects of many genes at different chromosomes together with the effect of environmental factors
What is an example of multi factor disorders?
-Diabetes, hypertension, obesity
What are the fundamental properties of cancer cells?
-Unregulated cell proliferation and metastatic spread
How does activation of oncogenes contribute to cancer?
-Proto-oncogenes become switched on and become hyperactive oncogenes
What do promo-oncogenes do?
-Stimulate cell division in response to specific signals
How does inactivating tumour suppressor genes contribute to cancer?
-In normal cells they block cell division at checkpoints of they are not ready and initiate apoptosis but in cancer cells this is permanently switched off
What happens in cancer cells that causes uncontrolled cell growth?
-Unable to stop cell cycle and enter G0 even with DNA damage and programmed cell death pathways are also inhibited
What are genetic polymorphisms ?
-Two or more existing different forms of DNA sequences in a certain gene within a population (at least 1%)
Where are polymorphisms found?
-Outside genes in DNA sequence that does not code for proteins
What are the functions of polymorphisms ?
-Determine the diversity of individuals and sometimes have a role in drug response, forensics or could represent risk factors for multi factor disease
What is gene expression?
-When a gene is turned on so protein synthesis occurs
What is epigenetic?
-The process of turning genes on or off
What does a histone and acetyl do?
-Acetylation-lowers attraction so DNA unwinds so open access to DNA strand is present
What happens to DNA when deacetylation occurs ?
-DNA is lock tight
What happens when there is one methyl group on a histone?
-Decreases attraction so unwinds DNA so DNA replication can take place
What happens if there is two or more methyl groups on a histone?
-DNA will repress and be lock tight so gene expression can not occur
What can adenosine be changed for during RNA editing?
-Inosine
What can cytosine be changed for during RNA editing?
-Uracil
How is a gene turned on?
-Enhancer is activated by the activator and bend over to the transcription factor
