Genetic Variation

Concept 6: Inheritable & Non-Inheritable Variation

Success Criteria

  • I can give examples of inheritable and non-inheritable variation.

  • I can explain how genes are inherited through reproduction.

  • I can compare the advantages and disadvantages of sexual and asexual reproduction.

  • I can explain the consequences of mutations that occur in gametes and somatic cells.

  • I can explain the importance of mutations in forming new alleles.

Vocabulary

Energy

Joule

Transformation

Hei Mahi

Vocab Bingo (with a Prize)

Step 1: Draw a 3 x 3 grid as your bingo chart.

Step 2: In each square, write a word from the list of vocab below.

homozygous heterozygous dominant recessive allele gene DNA genotype phenotype gamete
pedigree chart Punnett square

Step 3: Cross out the word once you hear Ms. Adviento read out its definition.

Step 4: Yell out "BINGO" once you have crossed out 3 words in a row (diagonals included).

Variation

Success Criteria:
I can give examples of inheritable and non-inheritable variation.

Variation exists in the features (traits) of individuals in a population.

Inheritable (genetic) variation

Some of this variation is genetic due to the different alleles carried by particular individuals.

  • For example in plants: Wrinkled pea shape allele

  • For example in animals: White coat allele

Genetic variations can be passed on to the next generation (they are inheritable variation).

Non-inheritable variation

Some variation is acquired due to environmental effects and/or the effects of an indvidual's actions.

  • For example in plants: Stunted growth from lack of nutrients.

  • For example in animals: Overfed (obese) domestic rabbit.

Acquired variations cannot be passed on to the next generation (they are non-inheritable variations).

Reproduction

Success Criteria:
I can explain how genes are inherited through reproduction.
I can compare the advantages and disadvantages of sexual and asexual reproduction.

Reproduction involves individuals passing on their genetic material (genes) to the next generation). There are two types: 1) Asexual reproduction, and 2) Sexual reproduction.

Reproduction is essential for the survival of a species. Some species reproduce only sexually. Others reproduce both sexually and asexually.

Asexual reproduction

Asexual reproduction involves one individual passing on its entire set of genetic material.

Offspring are genetically and phenotypically identical to each other and the parent (no variation). No new allele combinations are introduced into the population.

For example, identical aphids (one genotype and phenotype) are the result of asexual reproduction.

Advantages:

  • Reproduction is simple and rapid.

  • Population numbers can increase rapidly in ideal environmental conditions.

Disadvantages:

  • The lack of phenotypic variation, means the population is at risk of being wiped out in adverse environmental conditions.

Sexual reproduction

Sexual reproduction involves two individuals combining their genetic material.

Offspring are genetically unique, because new allele combinations are introduced into the population. (This is different to mutations). So it produces a variety of phenotypes.

Sexual reproduction gambles on new combinations of alleles (different phenotypes). Not every phenotype will be successful.

For example, varied rabbits (many phenotypes) are the result of sexual reproduction.

Advantages:

  • Some of the different phenotypes (variation) may survive adverse environmental conditions.

Disadvantage

  • Reproduction is slower, so the population cannot increase rapidly.

  • Reproduction takes more energy (need to find a mate).

Hei Mahi

Past Exam Question (2020 Q1)

Huntington's disease is a genetic disorder in humans. It is caused by a dominant affected allele (H). The normal allele is recessive (h).


a) Define genotype

b) Define phenotype

c) State the possible genotypes and phenotypes for Huntington's disease.

Mutations

Success Criteria:
I can explain the consequences of mutations that occur in gametes and somatic cells.
I can explain the importance of mutations in forming new alleles.

What is a mutation?

A mutation is a change in the base sequence of a gene found along a DNA molecule (chromosome).

Mutations may result in a new allele for a gene, which may code for a modified protein molecule.

Mutations are the only source of new alleles.

  • Some mutations are harmful as they code for modified proteins that don't function properly.

  • Occasionally, a mutation is beneficial, as it codes for a modified protein that functions better than the original.

Mutations are the ultimate source of genetic variation because they can result in new beneficial alleles within a population.

What causes mutations?

Mutations can be caused by exposure to mutagens (e.g. certain chemicals or radiation) or by an error in the replication of DNA just before a cell divides.

Are mutations inheritable?

If a mutation occurs in a body cell, then only those cells produced from this cell are affected. The mutation cannot be passed onto offspring.

If a mutation occurs in a gamete (sperm or egg), then the mutation can be passed on to offspring (but only if that particular gamete is fertilised.

Task 1: Worksheet assignment on Microsoft Teams

Task 2: SciPAD pages 221-225, 228-230

Task 3: Education Perfect task called Concept 6.

Hei Mahi

Past Exam Question (2020 Q2)

This is a pedigree chart for a family with a genetic disorder, polycystic kidney disease.

a) Complete a Punnett square for the cross between individual 1 homozygous recessive and individual 2 heterozygous.

b) List the genotypes of the following two individuals:

--- Individual 3

--- Individual 4

Concept 7: Mitosis & Meiosis

Success Criteria

  • I can describe the processes and products of mitosis and meiosis.

  • I can explain how independent assortment and crossing over increases genetic variation.

Vocabulary

diploid

haploid

meiosis

mitosis

Meiosis for Sexual Reproduction

Meiosis is the cell division that produces unique gametes (sperm or eggs) used in sexual reproduction. The daughter cells are haploid, meaning they have half the number of chromosomes.

Mitosis for Asexual Reproduction

Mitosis is the cell division that produces identical daughter cells used in asexual reproduction. The daughter cells are diploid, meaning they have a full number of chromosomes, identical to the parent cells.

Task 1: Worksheet assignment on Microsoft Teams

Task 2: SciPAD pages 226-227.

Task 3: Education Perfect task called Concept 7.

Concept 8: Natural Selection

Success Criteria

  • I can discuss why individuals in a population may have different probabilities of survival based on their phenotype.

  • I can explain the importance of variation within a population during a change in their environment.

Vocabulary

Energy

Joule

Transformation

Hei Mahi

Past Exam Question (2020 Q3)

Avian malaria is a parasitic disease affecting hoiho (yellow-eyed penguin), which can lead to death.

a) Describe genetic variation in hoiho.

Genetic Variation & Survival

Success Criteria:
I can discuss why individuals in a population may have different probabilities of survival based on their phenotype.

Genetic variation in a population refers to the different alleles (and combinations) existing amongst individuals in relation to particular traits. Genetic variation results in a variety of phenotypes within the population.

Genetic variation in a population is an advantage as it may help some individuals survive when there is a significant change in the environment. E.g. extreme drought, arrival of new predator, introduction of new disease.

Some phenotypes may be better suited to the new environment. Individuals with these phenotypes will live longer and produce more offspring. The surviving individuals pass on the favourable allele to their offspring. Over generations, the frequency of the favourable allele (and phenotype) increases, and the unfavourable allele decreases within the population.

Genetic variation increases the chances of a population surviving adverse environmental conditions. It may prevent a species from becoming extinct.

For example, a plant population has different alleles that give individuals different root lengths.

A drought occurs in a location occupied by a population of plants.

The individuals with an allele that gives them deep roots are more likely to survive the drought.

The surviving plants will breed with other survivors, producing more plants with deep roots.

For example, a rabbit population has different alleles that give individuals different levels of immunity to a disease.

A deadly new viral disease arises in a population of rabbits.

Some individuals have an allele that gives them immunity to this viral disease and they survive.

The surviving rabbits will breed with other survivors, producing more rabbits with immunity to the disease.

Adaptations & Natural Selection

Success Criteria:
I can discuss why individuals in a population may have different probabilities of survival based on their phenotype.

Adaptations are specific traits (aspects of the phenotype) that enable individuals to survive in a particular environment. Environmental factors like extreme droughts, arrival of a new predator or introduction of a new disease act as selection pressures. They 'weed out' individuals not well suited for current environmental conditions.

Selection pressures over many generations result in favourable phenotypes surviving and reproducing. Other, less favourable, phenotypes die off.

Click on this link to watch a video on Adaptations.

For example, some adaptations of cacti to survive areas of drought.

In this case, 'drought' is the selection pressure. Cacti with these adaptations will survive in reproduce, increasing the number of individuals with these adaptations in the population.

For example, some adaptations of arctic hares to avoid predators.

In this case, 'predators' are the selection pressures. Rabbits with these adaptations will survive and reproduce, increasing the number of individuals with these adaptations in the population

New phenotypes appear within a population as mutations and new combinations of alleles in sexual reproduction. Selection pressures will again act on these new phenotypes.

This ongoing process, where different selection pressures favour one phenotype over another, is called natural selection. This is the process by which a new population becomes adapted to its environment.

Click on this link to watch a video on the Recipe for Natural Selection.

Task 1: Worksheet assignment on Microsoft Teams

Task 2: SciPAD pages 231-236

Task 3: Education Perfect task called Concept 8.

Task 4: Explore the simulation below. Write a paragraph on how the simulation demonstrates natural selection.