B5 Genes, inheritance, and selection Flashcards
Definition of phenotype
- The physical expression of the genes
- The appearance of an organism
Give examples of genetic variation
Eye colour
Ear lobe
Ability to roll your tongue
Blood group
What are the two causes of variation?
- Genetic variation
- Environmental variation
What is genetic variation?
Variation caused by the genetic material you inherit from your parents
What is environmental variation?
Variation caused by the environment in you you live
What are the two types of variation?
Continuous variation
Discontinuous variation
Give examples of environmental variation
Accent
Dialect
Taste
Skills
Give an example of a characteristic that is affected by both environmental and genetic variation.
Height- it is mostly determined by your genes so if your parents are tall, you are also likely to be tall. However, if your diet is very poor you may not grow to your full potential height.
What causes continuous variation?
Genetic and environmental
Definition of continuous variation
continuous variation can take a value within a range
Genetic control in discontinuous variation
Genetic
Definition of variation
Difference within a species
What causes discontinuous variation?
Genetic
Definition of discontinuous variation
Discontinuous variation…
…can only result in specific (discrete) values
…characteristic that falls into distinct groups
What type of graph is used to display data for discontinuous data?
Bar chart
Examples of discontinuous variation
Gender
Eye colour
Wrinkled or non- wrinkled seeds
Blood group
Examples of continuous variation
Leaf surface area
Length of fur
Skin colour
Height
Definition of a clone
A clone is an organism that is genetically identical to its parent.
Genetic control in continuous variation
Multiple genes
What is asexual reproduction?
It involves one parent which means there is no mixing of genetic material so each new organism contains identical genes, which are genetically identical to the parent. This occurs by the process of mitosis.
Give examples of organisms that can reproduce asexually.
Bacteria
Potato plants- produce many tubers, each of which can grow into a new plant
Spider plants- produce long stems, known as runners, with tiny plants (plantlets) on the end.
Daffodils- produce an underground food storage organ (a bulb) at the end of each growing season. The following year a new flower will grow from a bud on this bulb.
Sea anemones
Star fish
What type of graph is used to display data for continuous variation?
Line graph
Histogram (often the bars are removed and just the line showing the trend shown)
What are somatic cells?
Cells that aren’t sex cells
Name an organism that can reproduce both sexually and asexually.
Sea anemones
Disadvantages of asexual reproduction
There is no genetic variation between offsprings so if the environment changes and the conditions become unfavourable, the whole population can be affected.
What are diploid cells?
Normal body cells (somatic cells)
They contain 46 chromosomes
Advantages of sexual reproduction
Creates genetic variation within the population which leads to adaptations. This means that if the environmental conditions change, it’s more likely that some individuals will have characteristics that enable them to survive. This leads to evolution as species become better adapted to their environment.
Disadvantages of sexual reproduction
- it take more time and energy than asexual reproduction as they need to find a mate so organism produce fewer organisms in a lifetime.
- Two parents are needed for sexual reproduction which can be a problem if the individual are isolated. Eg. Polar bears often live alone, so male polar bears may have to walk up to 100 miles to find a mate.
What is binary fission?
How bacteria reproduce.
What are haploid cells?
Gamete cells (ova and sperm cells) are haploid cells. They contain half the number of chromosomes of normal cells so 23 chromosomes.
Definition of genome
The entire genetic material of an organism
Where does meiosis occur in humans?
Ovaries and testes
Advantages of asexual reproduction
- Asexual reproduction can produce lots of offsprings very quickly as only one parent is involved so the organism does need to find a mate/partner.
- if the parent is well adapted to an rea, the offspring will share an identical set of characteristics.
What is a dominant allele?
It will always be expressed if they are present in its genetic material.
It is shown by a capital letter
Thought what process do zygote cells go through to produce new organisms?
Mitosis
How are gametes produced?
They are produced through a type of cell division called meiosis.
Definition of genotype
The combination of alleles present in an organism
What is a zygote?
It is diploid cells that is formed when during fertilisation two haploid gamete cells join together.
Definition of homozygous recessive
If you have two copies of the recessive allele. Eg. bb
Explain the first stage of meiosis.
1) Before the cell starts to divide the chromosomes are copied.
2) The chromosomes then line up in pairs in the centre of the cell. (One from the mother, one from the father)
3) The pairs are them pulled apart to opposite ends of the cell ( when they are pulled apart, often sections of DNA are swapped)
4) the cell than divides in two
5) Two separate cells are formed
Definition of alleles
Alternate forms of a gene
What is a recessive allele?
This characteristic is only expressed if you have two copies of the allele.
It is shown by a lower case letter.
Definition of homozygous dominant
If you have two copies of the dominant allele. Eg. BB
Explain the second stage of meiosis
6) In the second stage the chromosomes line up along the middle of each of the two new cells.
7) This time each chromosome is pulled in half. A single copy of each chromosome goes to opposite ends of the cell.
8) Each cell then divide into two. This results in four haploid cells.
Definition of heterozygous
If you have two different alleles for that articulate gene. Eg. Bb
What sex chromosomes so males have?
XY
So the father determines the sex of its offspring.
What affect do mutations have in coding DNA?
Mutations in coding DNA affect the proteins coded for by the gene. This can affect the protein’s structure and the way that is functions. Eg. The active site of an enzyme may be altered so that it can no longer bind with its substrate meaning it can no longer function.
What is a genetic variant?
It is a different version of an allele, which is caused by a change in the DNA. All variant arise from mutations.
What sex chromosomes do females have?
XX
What are sex chromosomes?
They are the 23rd pair of chromosomes in a human body cell.
Explain Gregor Mendel’s experiment on tall and dwarf pea plants.
1) Mendel crossed a tall pea plant with a dwarf pea plant. All the offspring were tall.
2) So, Mendel took two of the tall plants from the first set of offspring and crossed them. This time 75% off the offspring were tall but 25% were dwarf plants.
3) Mendel has shown that the height characteristic in pea plants was determined by separate inherited factors passed on from each parent. The ratios of tall and dwarf plants in the offspring showed that the factor for tall plants was dominant over the factor for dwarf plants.
Definition of mutation
A random inheritance to sequence of bases on DNA
It occurs when the sequence of DNA bases is altered.
Mutations can occur spontaneously
What affect do mutations have on non-coding DNA?
Mutations in non-coding DNA can affect how genes are expressed i.e whether or not genes are switched on. They can stop the transcription of mRNA so the protein coded for by that gene is not produced at all.
