3b - Inheritance Flashcards
What is a genome?
All genetic information (DNA) of an organism
What is a gene?
Small second of DNA that codes for a specific chromosome
What do gene code for?
Genes can code for Structural Proteins such as Collagen (skin), or Functional Proteins such as Haemoglobin
What does the nucleus contain?
Contains Chromosomes composed of Genes
What is a chromosome?
Carries genetic information (DNA) in a packaged and organised structure in functional pairs in Nucleus (The length of DNA supercoiled into a condensed mass.)
What are alleles?
They are a different version of gene. They code for the same characteristic but may give rise to a slight difference in that characteristic. E.g. there are 4 different allele of the hair colour gene (brown, black, blonde and red).
What does dominant mean?
Variant of a gene for particular characteristic that will always express itself whether it is partnered by Recessive Allele or by another like itself
What does recessive mean?
Variant of a gene for particular characteristic which will be masked or suppressed in presence of Dormant variant unless paired with another Recessive Gene
What does homozygous mean?
When an individual has two identical Alleles of a Gene
What does heterozygous mean?
When an individual has two different Alleles of a Gene
What does phenotype mean?
The characteristic that’s actually expressed
What does genotype mean?
The combination of alleles you actually have
What is polygenic inheritance?
Characteristics that are controlled by more than one gene are described as being polygenic.
Polygenic characteristics involves Phenotypes that can express a wide range of combinations in features
What is Monohybrid inheritance?
A monohybrid cross is the study of the inheritance of one characteristic.
- Recessive Allele is represented by a lowercase letter
- Dominant Allele is represented by an uppercase letter
What is a family pedigrees?
Chart of genetic history of a family over several generations
What are the rules for a family pedigree diagram?
- Males are represented as Squares, Females are represented as circles
- Shaded symbol indicates an individual is affected by stated condition, unshaded symbol indicates an individual is unaffected
My uncle has a square face
Girls have holes
Black people have black skin
White people don’t have black skin
What monohybrid crosses?
Determines the Allele combinations of offspring for one particular gene only
What is the method to do a monohyrbid cross?
STEP 1: Designate characters to represent Alleles
- Capital letter represents a Dominant Allele, lower case letter represents Recessive Allele
STEP 2: Write down the Genotype and Phenotype of the parents
- This is the Parental generation (P generation)
STEP 3: Write down the genotype of Parental Gametes
- This will be haploid as a result of Meiotic division
STEP 4: Use a Punnett grid to work out the potential gamete combinations
- As Fertilisation is random, all combinations have equal probability
STEP 5: Write out the Genotype and Phenotype ratios of potential offspring
- This is F1 generation (first filial generation)
Subsequent generations through interbreeding labelled F2, F3, etc
What is a diploid cell?
A diploid cell has two complete sets of chromosomes
What is a haploid cell?
A haploid cell has 23 chromosomes (sex cells)
What combinations of X and Y do females and males have?
Females possess two copies of the X Chromosome (XX)
Males possess one X and a shorter Y Chromosome (XY)
How is sex determined?
- Human sex determination occurs according to the X-Y system
- For Fertilised Embryo to develop into a Female, two copies of the X Chromosome are needed
- For Fertilised Embryo to develop into a Male, one copy of X and one copy of Y Chromosome is needed
- Hence, as all Female gametes (Egg cells) only carry copies of X Chromosomes, Male gametes (Sperm Cell) determines the sex of the offspring as they can carry either an X or Y Chromosome, therefore capable of producing a Male or a Female
What is a genetic diagram?
Means of determining all possible genetic characteristics of Offspring based on genetic characteristics of prospective parents
What is mitosis?
Cell Division that produces two genetically identical, diploid daughter cells
What is the function of mitosis?
- Tissue repair / replacement: Mitosis replaces damaged or aged cells with identical healthy cells
- Growth: Multicellular organisms increase in size and mass by increasing the number of cells via Mitosis
- Asexual reproduction: Vegetative propagation in plants occurs via Mitosis
- Development: Zygotes undergo Mitosis and differentiation to develop into Embryo
What is the process of mitosis?
- Prior to Mitosis, DNA replication occurs to form two copies of each Chromosome in cell
- Mitosis begins with the breakdown of Nuclear membrane, allowing the Chromosomes to line up across the centre of cell
- Fibres will then attach to each set of Chromosomes, pulling them to each end of the cell to form two individual Nucleus
- Cytoplasm and Cell Membrane then divides along with the Nucleus, resulting in two identical diploid daughter cells
What is meiosis?
Type of cell division that produces four haploid cells that are not genetically identical
What is the purpose of meiosis?
- Humans are composed of diploid cells, possessing two copies of each chromosome (one of Maternal origin, one of Paternal origin)
- Hence, for Humans to reproduce, Haploid gametes are needed that contain only one copy of each chromosome via Meiosis
- As a result, Fertilisation involves the fusion of two haploid gametes (Egg from Mother, and Sperm from father), resulting in the formation of diploid Zygote that will develop into an Embryo
How many stages of mitosis are there?
2
What is genetic variation?
Difference in DNA Sequence of Individual offsprings from the same parent or species
What causes genetic variation?
- Genetic variation in offsprings are a result of random fertilisation, meiosis and mutations
- With meiosis resulting in genetically distinct gametes, the random fertilisation of an Egg cell by a single Sperm (out of over millions of Sperm cells) will further produce genetically distinct Zygotes
- As a result, offsprings will show increased genetic variation
-Genetic variation may also result from mutation, involving a change in DNA sequence to produce new Alleles for a specific trait
How many chromosomes in a diploid and haploid cell? are they produced via mitosis or meiosis?
diploid : 46 - mitosis
Haploid : 23 - meiosis
What are some examples of diploid and haploid cells?
diploid: Skin cells, Red blood cells
haploid: Sex cells
What is variation?
Difference in DNA Sequence of Individual offsprings from the same parent or species
What is variation?
Difference in DNA Sequence of Individual offsprings from the same parent or species
What are the 2 factors that can effect variation?
genetics and environmental
What are genetic factors?
Variation in species can be caused by genetic factors via inheritance of Alleles from Parents for certain characteristics
What are environmental factors?
Variation in species can be caused by environmental factors that places pressure on organisms to adapt or change to aid their survival, allowing them to be better suited to their environment
What are some examples of genetic factors?
- Eye colour
- Hair colour
- Blood type
- Inherited disorders
What are some examples of environmental factors?
- Resource availability - presence of sufficient food, habitat and mates
- Environmental conditions - temperature, weather conditions or geographical access
- Biological factors - predators and pathogens)
Can variation be caused by both genetic and environmental factors?
- Variation can be influenced by both genetic and environmental factors
- While genes determine the characteristics that are inherited by an individual, environmental factors can influence how the inherited characteristic develops
What are some examples of characteristics that are affected by both genetic and environmental factors?
PLANTS
- Plants may inherit genes that allow strong growth
- However, if they do not receive sufficient mineral resources from the soil, this characteristic cannot be expressed
2. CHILD - Child may inherit genes for the tendency to be tall - However, a poor diet during childhood will cause poor growth, preventing this characteristic from being expressed
What is mutation?
Rare and random change in DNA sequence coding for new alleles for gene
What are the 3 different types of variation?
- Beneficial Mutations
- Detrimental Mutations
- Neutral Mutations
What is a beneficial mutation?
Beneficial Mutations change DNA sequence to create new variations of trait that makes organism better adapted to environment, increasing chances of survival
What is a detrimental mutation?
change DNA sequence to truncate DNA sequence to abrogate normal function of trait
What is a neutral mutation?
Neutral Mutations has no effect on the functioning of specific characteristics
What is the meaning of evolution?
Gradual change of species over long periods of time
What does natural selection mean?
Process where organisms that are better adapted to an environment will survive and reproduce to pass on genes to next generation
What is Darwins theory?
- Individuals in a Species show a range of variation caused by differences in genes
- Individuals with characteristics better adapted to the environment have a higher chance of survival, allowing them to reproduce
- These genes are passed onto their offspring, showing evolution of species via natural selection
what does VOSSIG stand for?
V = variation – individuals within a species show variation
O = Overproduction – all organisms overproduce
S = Struggle for existence (competition) – competition for recourses
S = Survival of the fittest – those best adapted will be more likely to survive and reproduce
I = Inheritance – those who survive and reproduce pass on their alleles
G = Gradual change – over many generations the population will change.
VOSSIG example:
- Organisms within the population will show variation via mutations
- Mutated organism that has characteristics allowing them to be better adapted to the environment will have higher a chance of survival
- Hence, they will reproduce to pass on these beneficial mutations to offspring
- As a result, offspring will carry the same beneficial gene, allowing the population over time to be better adapted to environment - evolution via natural selection
What are antibiotics?
Drugs that can kill bacteria without affecting our cells.
What are the problems with antibiotics?
- They have been commonly used for years
- They have been misused
- This had led to antibiotics resistance
How antibiotics resistance occurs:
- You start taking antibiotic
- Some bacteria are susceptible to (killed by) the antibiotic. Some are resistant to (not killed by) antibiotic
- The susceptible (weak) bacteria are killed first
- Only resistant (strong) bacteria are left.
- You stop taking the antibiotic
- The resistance (strong) bacteria reproduce
- The resistant (strong) bacteria are now more common
- If you take the antibiotic again, it won’t work because all the bacteria are resistant
