Genetics Flashcards
What is DNA?
the molecule that contains the genetic information used in the development and functioning of all living organisms
What are chromosomes?
dense structures of tightly coiled DNA that become visible during division
What is a gene?
-a sequence of DNA that functions as unit of genetic information
-this section is located between a start codon and stop codon
What is a genotype?
the genetic total extent of the genetic information we carry
What is a phenotype?
this is what genetic information is actually expressed in our physical appearance or outward characteristics
What does each chromosome form?
chromosome pairs, therefore we have a pair of genes of each characteristic
What are alleles?
alternative versions of the same gene
What does homozygous and heterozygous mean?
-homozygous= person carries the same allele on each homologous chromosome
-heterozygous= person carries different alleles on each homologous chromosome
Explain the process of protein synthesis
- information contained in a specific region of DNA is copied (transcribed) to produce a specific molecule of RNA
- RNA attaches to a ribosome where the information in the RNA is translated into specific amino acids to form a new protein molecule
What is a triplet codon?
three bases which carry the genetic code of instructions which codes for a single amino acid
What are the 3 types of RNA made from DNA?
-Messenger RNA (mRNA)
-Ribosomal RNA (rRNA)
-Transfer RNA (tRNA)
What is inheritance?
the passage of hereditary traits from one generation to the next
How many pairs of chromosomes does the nuclei of all human cells contain?
23 pairs (the diploid number) , one chromosome in each pair came from the mother and one from the father
What are the 4 nucleotide bases in DNA?
Adenine
Guanine
Cytosine
Thymine
What is a complementary strand of DNA?
-the nucleotides bind in pairs: A binds with T, and C binds with G
-therefore the coding strand and complementary strand are made up of these complementary matches
What does the process of mitosis produce?
two genetically identical daughter cells that have the same number of chromosomes as the original cells
What does the process of meiosis produce?
four daughter cells that have half the number of chromosomes as the original cell, all genetically different
What is the difference between dominant and recessive alleles and how are these expressed in a punnet square?
-where 2 different alleles may be present in the genotype, usually one is dominant and becomes expressed in the phenotype, and one is recessive and remains dormant within the genotype
-dominant alleles are abbreviated with a capital letter e.g T and recessive alleles are abbreviated with a lowercase letter t
-you have to have 2 recessive alleles for the recessive genotype to be expressed
What is phenylketonuria (PKU) and what type of condition is this?
-condition where unable to produce enzyme phenylalanine hydroxylase (PAH) due to non functional allele for this enzyme causing problems with metabolism and neuronal developement
-its an autosomal recessive, therefore there’s a 25% chance in developing the condition (aa)
What is Huntingdon’s disease and what type of condition is this?
-a genetically inherited disease of the brain that damages nerve cells causing a gradual deterioration in cognitive function
-its a autosomal dominant condition
-50% will develop the condition and 50% will be unaffected
what is a sex linked condition giving an example
-these conditions are found on the sex chromosomes, XX = girl, XY= boy
-red green colour blindness are unable to distinguish shades of red and green
-as this condition expresses its allele on the X chromosome, males only need one defective allele for the condition to develop
What is co-dominance?
some genes may not show complete dominance but rather share the phenotype between two alleles e.g AB blood group
What is genetic imprinting?
involves a sex-specific process of chemical modification to the gene so that the alleles are unequally expressed depending on the sex of the parent carrying the modified gene
What does polygenic mean?
most often several genes are responsible for any given trait e.g skin colour
what does multifactorial mean?
they involve a complex interaction of the genes with the environment
What is epigenetics?
-the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself
What modifications can be made to gene expression?
adding molecules e.g methyl groups to DNA, changing the structure of DNA but not the sequence, altering how the gene interacts during transcription
What is genetic counselling?
a service that provides support, information and advice about genetic conditions
Give examples of what genetic counselling includes
-providing information on the genetic condition that affect the family
-calculating risk of passing inherited condition to their children
-discussing risks, benefits and limitations of genetic testing
