4. Genetics Flashcards
What is meant by genome
All the genetic material of an organism
What are chromosomes
Genetic structures that function in pairs
they are found in the nucleus of a cell
They are made up of genes and DNA
What is a gene
A section of a chromosome that control a particular characteristic eg hair colour
What is an allele
Different forms of the same gene e.g. gene for hair colour may have a brown hair allele, blond hair allele, black hair allele
What is DNA
made up of nucleotides that are joined together by the sugar - phosphate back bone
What are the 4 types of bases found on a nucleotide
A, T, G, C
What base pairs occur between bases of nucleotides
A base pairs with T
G base pairs with C
How does DNA work
DNA codes for the order of the amino acids in a protein
The base code is always in groups of 3 - known as the triplet code
If a gene has 54 bases along its coding strand for a protein. How many amino acids make up the protein
1 amino acid -= 3 bases
54/3 = 18 amino acids
What is the shape of DNA called
Double Helix
What are the most common proteins DNA produce
Enzymes - which control the development of a cell
What happens in mitosis
Mitosis is cell division to produce replacement cells, repair cells or for growth
Before division the chromosomes in nucleus make a complete copy of themselves
They line up at the middle of cell and then divide into 2 daughter cell
Each daughter cell has exactly the same number of chromosomes as the original (diploid cells)
What is meiosis
Cell division that happens to produce gametes - sperm and egg cells
Before division chromosomes duplicate (double the number)
Involves 2 cell divisions
Produce 4 daughter cells that have half the genetic information as the original cell (haploid cells)
What is independent assortment in meiosis
How the chromosomes separate the pairs of chromosomes is random so can lead to variation in the combination of each chromosome in each gamete
Why is meiosis important
When the sperm and egg join at fertilisation it ensures that the diploid number of chromosomes (23 pairs) is restored
What is meant by a dominant allele
The characteristic that the dominant allele codes for will be expressed even if only one allele is dominant - if the person is heterozygous or homozygous dominant
What is meant by a recessive allele
The characteristic that the recessive allele codes for will ONLY be expressed if both alleles are recessive - homozygous recessive
What is meant by heterozygous
Alleles are different e.g. Bb
What is meant by homozygous
The alleles are the same eg BB, bb
What is meant by genotype
The genetic combination of the pair of allele eg Bb
What is phenotype
The feature/characteristic that the genotype will produce
eg. Bb genotype results in brown hair (phenotype)
What is the name of the drawing you do too show a genetic cross
Punnett square
What would be the outcome ratio if both parents are heterozygous eg Bb
Bb x Bb
gametes are B or b
Complete punnett square
Offspring - 1 BB, 2Bb, 1bb
Ratio 1:2:1
or 3:1 ratio have dominant feature
What is a test cross
This is when you want to find out if the organism with the dominant characteristic is heterozygous or pure breeding (homozygous dominant)
Complete cross with a homozygous recessive (as know its genotype)
If all offspring are dominant featured then the parent is homozygous dominant
e.g BB x bb = all offspring Bb
If half of the offspring have the recessive feature then they are heterozygous
Bb x bb = 2Bb: 2bb
What is a pedigree diagram
A type of family tree in which you can work out the genotype of people using information provided
Who was Mendel
Mendel studied peas and developed the laws of genetics by doing crosses between different characteristics
What causes Cystic Fibrosis
A recessive allele
parents could be carriers (heterozygous Cc) and pass the allele onto a child
Cc x Cc
1 CC, 2Cc and 1 cc - with the condition
What causes Huntingtons Disease
A dominant allele
Person may already have children before know they have the condition
Can be heterozygous an still have condition
What is haemophilia
A sex linked condition found on the X chromosome (recessive condition)
Males more likely to get condition as only inherit 1 X chromosome
XhY
What is Downs Syndrome
Caused by a chromosome mutation
Person gets extra chromosome on pair 21
Have 47 rather than 46 chromosomes
What is genetic screening
If a person knows a condition in family tree may wish to test to see if they have the condition
Common - used in diagnosing Downs Syndrome - doing an amniocentesis
Taking sample of amniotic fluid and growing the cells in it (from foetus)
Seeing if have 47 chromosomes
Ethical issues - person may then abort the child
What is genetic engineering
Removing the gene from one organism and inserting into another organism
e.g. insulin
Removing insulin from chromosome using Restriction Enzymes
Cutting open plasmid DNA of bacteria using restriction enzyme
inserting gene into the plasmid
Placing the genetically modified plasmid into the host (bacteria)
They reproduce and all bacteria have the gene for making insulin
What processes happen in downstreaming
Extraction
Purification
Packaging (of insulin)
What is a bioreactor
The container that grow bacteria in to produce insulin - conditions monitored e.g. pH, oxygen , glucose
Surrounded by cooling jacket to remove heat released during respiration
Mixed with stirrer to keep bacteria in contact with food and ensure aerobically respiring
