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).
What is a pedigree diagram used for?
To determine the probability of inheriting a genetic disease within a family tree.
What does a pedigree diagram not indicate?
It does not reveal whether individuals are carriers of the disease or if the disease is recessive or dominant.
How are males represented in a pedigree diagram?
Squares
How are females represented in a pedigree diagram?
Circles
What does a shaded symbol indicate in a pedigree diagram?
Affected
What does an unshaded symbol indicate in a pedigree diagram?
Unaffected
Sepal
Protects unopened flower
Petals
Brightly coloured in insect-pollinated flowers to attract insects
Anther
Produces and releases pollen
Filaments
Provides support to the anther
Stigma
Sticky top of the female part of the flower which collects pollen grains
Style
A tube that connects the stigma and ovary
Ovary
Contains the ovules
Ovule
Structures inside the ovary that contain the female gametes
Where are the male gametes of plants found?
Male gametes are found in pollen grains.
Where are the female gametes of plants located?
Female gametes are found in ovules.
What is pollination?
Pollination is the transfer of pollen from the male part of a flower to the female part.
What happens when an insect enters a flower?
It brushes against the anthers, which deposit sticky pollen onto the insect’s body.
What occurs during pollination when the insect visits another flower?
The insect brushes against the stigma, depositing pollen from the first flower.
What is the adaptation of petals in insect-pollinated flowers?
Large & brightly coloured petals attract insects.
Why do insect-pollinated flowers produce scent and nectar?
To encourage insects to visit the flower & push past the stamen to access the nectar.
How are anthers adapted for insect pollination?
Held on stiff filaments within the flower so that they brush against insects
What is the role of the stigma in insect-pollinated flowers?
The sticky stigma catches pollen grains when insects brush past it.
How are the anthers and stigmas of wind-pollinated flowers adapted for pollination?
They hang outside the flower on long filaments to:
-Allow pollen to be easily blown away by the wind.
-Help stigmas catch airborne pollen.
What is the adaptation of petals in wind-pollinated flowers?
Small and dull, often green or brown in colour; producing colourful petals would be a waste of energy
Why don’t wind-pollinated flowers produce scent and nectar?
Unnecessary, so their production would be a waste of energy.
How are the anthers adapted in wind-pollinated flowers?
Anthers are held on long filaments outside the flower to release pollen easily into the wind.
How are the stigmas adapted in wind-pollinated flowers?
Feathery stigmas outside the flower help to catch airborne pollen.
What are the offspring called when produced by asexual reproduction?
The offspring are called clones because they are genetically identical to the parent.
Runners
-A new plant grows where the runner touches the ground.
Tubers
-Swollen underground stems store food
-1 plant produces many tubers that each grow multiple shoots, forming new plants.
Bulbs
-Bulbs are underground buds with thick, fleshy leaves that contain stored food.
-A main shoot grows from the parent bulb, and side ‘daughter’ bulbs can also grow, forming 2 plants.
What are natural methods of asexual reproduction in plants?
Runners, tubers, bulbs
What are artificial methods of asexual reproduction in plants?
Cuttings
What is the method of growing plants from cuttings?
-Cut a piece of the stem with a few leaves from a healthy plant.
-Plant the cutting in damp compost.
-The cutting will grow roots and develop into a new plant.
What is the role of oestrogen in the menstrual cycle?
-Oestrogen levels rise from day 1 to peak just before day 14
-Thickens uterus lining
-Inhibits FSH and LH release
What is the role of progesterone in the menstrual cycle?
-(Progesterone stays low from day 1 – 14 and starts to rise once ovulation has occurred)
-Thickens uterus lining
-Inhibits FSH and LH
What is the role of FSH (follicle-stimulating hormone) in the menstrual cycle?
-Matures the follicle
-Triggers oestrogen release
What is the role of LH (luteinising hormone) in the menstrual cycle?
-Causes ovulation
-Triggers progesterone release
Describe how hormones control the menstrual cycle
-FSH stimulates the maturation of the follicle/egg/ovum
-Oestrogen inhibits FSH and stimulates LH
-LH stimulates ovulation
-Progesterone inhibits FSH and LH
-Oestrogen and progesterone maintain/thicken the lining of the uterus
The green aphid lives on rose bushes in the UK in the summer. In spring, aphids that are hatched from eggs are all female. They can produce offspring without male aphids.
i. Name the type of reproduction that these female aphids carry out to produce offspring.
ii. Describe how the offspring will compare to the parent aphid
i. Asexual reproduction
ii. Offspring will be genetically identical to parent
What happens after fertilization in the oviduct?
-The zygote divides to form an embryo.
-The embryo travels to the uterus.
-Upon reaching the uterus, the embryo implants in the uterine lining to continue developing.
What is the function of the placenta?
-Enables the exchange of substances between the mother’s blood and the fetus’s blood.
-Connects the embryo’s blood supply to the placenta via the umbilical cord.
What substances travel from the mother’s blood to the fetus?
-oxygen
-nutrients, e.g. glucose, amino acids and mineral ions
What substances travel from the fetus’s blood to the mother?
-carbon dioxide
-urea
Why is the placenta an efficient exchange surface?
because it has:
-a large surface area
-a thin wall for efficient diffusion
What is one of the key functions of the placenta?
-Acts as a barrier to toxins and pathogens.
-Helps protect the developing fetus from harmful substances.
The green aphid lives on rose bushes in the UK in the summer. In spring, aphids that are hatched from eggs are all female. They can produce offspring without male aphids.
i. Name the type of reproduction that these female aphids carry out to produce offspring.
ii. Describe how the offspring will compare to the parent aphid
i. Asexual reproduction
ii. Offspring will be genetically identical to parent
What surrounds the developing embryo in the uterus?
-The developing embryo is surrounded by amniotic fluid.
-This fluid is contained within the amniotic membrane (or amniotic sac).
What is the function of amniotic fluid?
-Protects the embryo during development.
-Cushions the embryo from bumps & movements of the mother.
