B13 - Reproduction Flashcards
What happens in sexual reproduction? Give some examples of where it occurs:
-fusion of male + female gametes, with mixing of genetic information to produce variety in the offspring
-sperm/egg cells in animals
-pollen/egg cells in flowering plants
Give some advantages of sexual reproduction:
-we can use it to speed up natural selection with selective breeding to increase food production
-variation produced in offspring
-gives survival advantages by natural selection if the environment changes
What does asexual reproduction involve?
-1 parent reproducing by mitosis with no fusion of gametes
-leads to genetically identical offspring (clones)
Give 3 advantages of asexual reproduction:
-occurs faster
-time/energy efficient, as no need to find a mate (only 1 parent needed)
-many identical offspring can be produced when conditions are favourable
What is the difference between the products of mitosis and meiosis?
Give numbers of chromosomes
-mitosis forms 2 genetically identical diploid cells with 46 chromosomes each (23 homologous pairs)
-meiosis forms 4 genetically varied gamete haploid cells with 23 chromosomes each
Give 2 similarities between mitosis and meiosis:
-DNA gets replicated in both
-number of sub-cellular structures increase in both (mitochondria/ribosomes)
What causes the cells produced in mitosis to be genetically identical?
DNA gets duplicated
Explain how chromosomes are arranged in the cell’s nucleus:
the cell has one of each type of chromosome from the mother and the father, and is arranged into 23 homologous pairs (46 individual chromosomes)
When genetic material is duplicated, what does that actually mean in terms of chromosomes?
-each chromosome from the homologous pair makes another identical arm connected to it
-the number of individual chromosomes stays the same though
Describe the process of meiosis:
-genetic info is duplicated
-homologous pairs line up along the middle of the cell and separate (rather than each chromosome lining up) into 2 cells
-in each cell, their 2-armed chromosomes line up along the middle and each arm separates from each other
-both cells divide again, forming 4 non-identical haploid cells
Name 3 specific examples of organisms that reproduce by both sexual and asexual methods:
-malaria parasites - asexually in human host, sexually in mosquito
-most fungi - asexually by spores, and sometimes sexually to give variation
-most plants - asexually by runners (in strawberries) or bulb division (in daffodils), and sexually by seeds
Bluebells can reproduce sexually by seeds - explain why this would prove to be a survival advantage for them:
-genetic variation so the better-adapted survive
-can colonise new areas by seed dispersal
-can escape adverse event in original area by continuing to live in other areas
How is genetic information stored in a body cell? Describe its structure:
-in DNA, a 2-chained polymer of 4 different nucleotide monomers with a double helix shape
-within thread-like structures called chromosomes
-all the chromosomes make up the genome
What is the genome?
the entire genetic material of an organism
Why is it important to understand the human genome?
-can diagnose/treat inherited disorders
-can trace human migration patterns from the past
-can search for genes linked to different types of diseases