Inheritance Flashcards
Give one difference between mitosis and meiosis.
Mitosis leads to genetically identical cells being formed while meiosis leads to non- genetically identical cells being formed.
What does sexual reproduction involve?
The joining (fusion) of male and female gametes.
Give examples of male and female gametes.
-Sperm and egg cells in animals
-Pollen and egg cells in flowering plants
What does the mixing of genetic information lead to in sexual reproduction?
Variety in the offspring.
What does the formation of gametes involve?
Meiosis
What does asexual reproduction involve?
Only one parent and no fusion of gametes.
Only mitosis (a cell dividing in 2)
Why does asexual reproduction lead to genetically identical offspring?
There is no mixing of genetic information hence genetically identical offspring.
Explain how meiosis halves the number of chromosomes in gametes (sex cells).
Each pair of chromosomes replicate and the cell splits in two. There are now two genetically identical cells.
The diploid cells divide again. Chromosomes are distributed between the new cells at random.
This creates four genetically different gametes which each have half the number of chromosomes than in the parent cell.
Explain how fertilisation restores the full (normal) number of chromosomes.
Gametes join/fuse at fertilisation.
The maternal chromosomes from the egg cell and the paternal chromosomes from the sperm cell pair up to form a zygote with the full number of chromosomes.
Cells in reproductive ______ divide by ______ to form ________.
organs
meiosis
gametes
Explain what happens when a cell divides to form gametes.
-copies of the genetic information are made (chromosomes duplicate)
-the cell divides twice to form four gametes, each with a single set of chromosomes
-all gametes are genetically different from each other.
What does the new cell formed by the fusion of two gametes (zygote) do?
Divide by mitosis.
This causes the total number of cells to increase, forming a ball of cells called an embryo.
As the embryo develops, cells differentiate.
List the advantages of sexual reproduction.
-Produces variation in the offspring as the organism inherits alleles from both parents
-If the environment changes, variation gives a survival advantage (increased chance of survival) by natural selection.
Natural selection can be speeded up by humans in selective breeding to produce what?
(Advantage of sexual reproduction)
Animals with desired characteristics.
They are bred to produce offspring which inherit the desired characteristics.
e.g. animals that produce a lot of meat can be selectively bred to increase food production.
Natural selection
Individuals with characteristics that make them better adapted to an environment have a better chance of survival.
They are therefore more likely to breed successfully and pass the genes for the characteristics on.
List the advantages of asexual reproduction.
-Only one parent is needed
-More time and energy efficient as organisms do not need to find a mate
-Faster than sexual reproduction
-Many identical offspring can be produced when conditions are favourable.
Asexual vs Sexual reproduction links to what topics?
-Animal and plant cells
-Cloning
Which organisms can reproduce by both sexual and asexual reproduction depending on the circumstances?
-Malarial parasites
-Fungi
-Plants like strawberries and daffodils
Reproduction in malarial parasites.
Malaria is caused by a parasite that’s spread by mosquitos.
When a mosquito carrying the parasite bites a human, the parasite can be transferred to the human making them sick.
The parasite reproduces sexually in the mosquito (the vector), but asexually in the human host.
Reproduction in fungi
Many fungi reproduce asexually by spores, which can become new fungi when they land in a suitable place.
Spores can also be produced sexually to give variation.
This is usually in response to an unfavourable change in the environment, to increase the chance of the population surviving the change.
Reproduction in plants
Many plants produce seeds sexually (pollen deposited on stigma and egg in pistil), but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils.
Define genome.
The genome of an organism is the entire genetic material of that organism.
The whole human genome has now been studied and this will have great importance for what in the future?
medicine!!
Describe the structure of DNA
DNA is a polymer made up of two strands forming a double helix.
The strands are made of many repeating monomer units called nucleotides.
Each nucleotide consists of a common sugar and phosphate group with one of four different bases (A,T,C, or G) attached to the sugar.
The long strands themselves consist of alternating sugar and phosphate sections.
The bases A and T, C and G pair to join the strands.