Genetics Flashcards
What is a DNA double helix
Deoxyribose ( sugar )
Nucleic ( nucleotides )
Acid ( phosphate)
What is the location and function of DNA
Found in nucleus
Carries all of our genetic material
Describe the idea of nucleotides
Made up of 4 bases - adenine & thymine or guanine & cytosine
Adenine always pairs with thymine
Guanine always pairs with cytosine
Describe the backbone of DNA
Nucleotides are linked together via the phosphate to form the back bone
Describe the pattern of pairings with bonds
A-T are bonded using 2 hydrogen bonds
C-G have 3 hydrogen bonds between them
Describe the replication process
DNA strand is unzipped by helicase which breaks the hydrogen bonds between the base pairs
The enzyme primase starts the process of rebuilding the separated strands
Primase makes a small piece of RNA which is a primer
DNA polymerase binds to primer to make new strands
What is RNA
Has a backbone made with alternating phosphate groups and ribose which is different to DNA
Attached to each sugar in one of four bases - adenine, uracil, cytosine or guanine
Found in cells nucleus, cytoplasm and organelles
What are chromosomes
Bundles of DNA
Tightly coiled strand of DNA around a histone
Histones are proteins which give structure to the long strand of DNA
How many chromosomes are there
Most cells in the body contain 46 chromosomes and are in 23 homologous pairs
22 pairs are autosomal and the 23rd pair is sex determing
What are diploid cells
All cells in the human body are diploid minus sperm and egg cells
Contain all of the genetic material
Contain the normal amount of pairs of chromosomes
Produced from identical versions of themselves
Reproduce identical versions of themselves
What are haploid cells
Sperm and egg cells
Contain half of genetic material
Contain 23 chromosomes not pairs
Made by diploid cells via meiosis- producing 4 non identical versions of the cell
Each cell has a different set of genetic material so they aren’t exact copies
What is a gene
Section of DNA that codes for a particular protein
Explain genes and codons
There are between 20,000 - 25,000 genes in the human genome
Genes are made up of a series of nucleotide bases in a chain, from a few hundred to 2 million per gene
Codons are much smaller units and are chains of three base groupings
What are alleles
Different versions of the same gene
If two alleles are identical are called homozygous
If two alleles are different are called heterozygous
What are mutations
Alteration of bases in the genetic code
What are single gene disorders
Autosomal dominant
Autosomal recessive
Sex linked recessive
Sex linked dominant
What does autosomal and sex linked mean
Autosomal refers to the 22 non sex chromosomes
Sex linked refers to the 1 set of XX or XY chromosomes
Show how to see dominant and recessive
R is dominant
r is recessive
What is a phenotype
Observable physical property of an organism
What are examples of autosomal dominant disorders
Achondroplasia ( dwarfism )
Huntingdon’s disease
Neurofibromatosis
Osteogenesis imperfecta
What are examples of autosomal recessive disorders
Sickle cell
Thalassemia
Cystic fibrosis
Phenylketonuria (PKU)
Medium chain acyl CoA dehydrogenase deficiency (MCADD)
How can someone have an autosomal recessive disorder
If both parents are carriers or have the condition for it to be present
What are examples of X linked recessive disorders
Haemophilia
Duchene muscular dystrophy
Colour blindness
What are examples of X linked dominant disorders
Fragile X
What are examples of Y linked disorders
Related to male infertility
What is co- dominance inheritance
Some genes may not show complete dominance but rather share the effect between the two alleles e.g. sickle cell disease
What is multiple allele inheritance
Some genes have more than two alternate forms e.g. ABO blood groups
What is polygenic inheritance
Most often several genes are responsible for any given trait e.g. eye colour
Diseases such as heart disease
What is multifactorial inheritance
Since they involve a complex interaction of the environment e.g. cigarette smoke
