Reproduction and inheritance Flashcards
What is sexual reproduction?
-The fusion of the nuclei of two gametes to form a zygote (fertilised egg cell).
-Produces genetically different offspring.
How many parents are required for sexual reproduction?
2 parent organisms
What types of cell division are involved in sexual reproduction?
-Meiosis produces gametes.
-Mitosis occurs after fertilisation to develop the zygote.
How are offspring genetically related to their parents in sexual reproduction?
-Offspring inherit half of their DNA from each parent.
-They are genetically different from the parents and from each other.
What is a survival advantage of sexual reproduction?
Genetic variation provides greater adaptability to environmental changes.
How fast is sexual reproduction compared to asexual reproduction?
It is a relatively slow process.
What is asexual reproduction?
The production of genetically identical offspring from one parent.
Does asexual reproduction involve gametes or fertilisation?
No, there are no gametes, no fertilisation, and no genetic mixing.
How are offspring related to the parent in asexual reproduction?
Offspring are genetically identical to the parent (they are clones).
What is the advantage of asexual reproduction?
It is faster and more efficient than sexual reproduction.
What is a disadvantage of asexual reproduction?
Lack of genetic variation makes populations more vulnerable to disease or environmental change.
What is binary fission?
A type of asexual reproduction in bacteria where they produce exact genetic copies of themselves.
How many parents are required for sexual and asexual reproduction?
Asexual: One
Sexual: Two
What type of cell division is used in each reproduction method?
Asexual: Mitosis
Sexual: Meiosis (for gametes) and Mitosis (after fertilisation)
How similar are offspring to the parents in each reproduction method?
Asexual: Genetically identical to the parent.
Sexual: Genetically unique from both parents.
What are the sources of genetic variation in sexual reproduction?
-50% DNA from each parent.
-Meiosis, resulting in new combinations of alleles.
-Random assortment of chromosomes during meiosis.
How many offspring are typically produced in asexual vs. sexual reproduction?
Asexual: Large numbers.
Sexual: Limited numbers.
How does the time taken to produce offspring compare between sexual & asexual reproduction?
Asexual: Relatively fast.
Sexual: Relatively slow.
What is a gene?
-a short length of DNA found on a chromosome that codes for a particular characteristic
What is an allele?
-a variation of a gene
How many copies of each chromosome do we have?
-2 copies of each chromosome (one from each parent).
How do different alleles affect inherited characteristics?
-Different alleles can code for varied traits; for example, one allele for eye colour may code for brown eyes while another may code for blue eyes.
-This leads to variation within species.
Dominant
A dominant allele is always expressed, even if only 1 copy is present
Recessive
A recessive allele is only expressed if 2 copies are present (therefore no dominant allele present)
Homozygous
If the 2 alleles of a gene are the same, we describe the individual as being homozygous (homo = same).
Heterozygous
If the 2 alleles of a gene are different, we describe the individual as being heterozygous
(hetero = different).
Genotype
The combination of alleles that control each characteristic is called the genotype.
Phenotype
The observable characteristics of an organism (seen just by looking - Like eye colour, or found through testing - Like blood type)
Monohybrid inheritance
The inheritance of characteristics controlled by a single gene.
How are dominant and recessive alleles represented in a Punnett square?
Dominant allele: Capital letter (e.g., T)
Recessive allele: Same letter in lowercase (e.g., t)
What are the steps for constructing a Punnett square?
- Determine parental genotypes.
- Select a distinct letter pair for alleles (e.g., Aa, Bb).
- Split the alleles for each parent and place them around the outside of the Punnett square.
- Fill in the middle squares to find possible genetic combinations.
What is meant by ‘pure breed’?
An individual that is homozygous for a characteristic (e.g., TT or tt).