Reproduction and Inheritance Flashcards
What are human body cells?
diploid
What does diploid mean?
The cells have two copies of each chromosome, arranged in pairs
How many chromosomes does a human cell nucleus contain?
46
What is the diploid number for a human?
46
What is DNA
A list of instructions on how to put an organism together and make it work
What is each separate gene in a DNA molecule?
A chemical instruction that codes for (says how to make) a particular protein
Why are proteins important?
They control most processes in the body and determine inherited characteristics
What are alleles?
Different versions of the same gene
What structure is DNA?
A double helix
What are the two strands in DNA held together by?
chemicals called bases
What are the four different bases?
Adenine
Cytosine
Guanine
Thymine
What is the pairing of the bases? And what is it called?
A-T and C-G
complimentary base-pairing
DNA is a type of…
nucleic acid
What hold the pairs of bases together?
hydrogen bonds
A sequence of three bases codes for…
an amino acid
What are the two types of cell division?
meiosis and mitosis
When does mitosis occur?
in asexual reproduction and growth and repair
What are the end products of mitosis?
Two cells containing exactly the same DNA (genetically identical)
What is mitosis?
When a cell reproduces itself by splitting to form two cells with an identical set of chromosomes
What does meiosis produce?
Four haploid cells whose chromosomes are NOT identical
Sexual reproduction involves…
the fusion of male and female gametes
What are gametes?
sperm cells and egg cells
What are gametes like in comparison with normal cells in terms of their chromosomes?
haploid - they have half the number of chromosomes in a normal cell
In humans, each gamete contains how many chromosomes?
23
What is another name for a fertilised egg?
A zygote
What does a zygote develop into
an embryo
Is the fertilisation of gametes random? and what does this produce?
YES, this produces genetic variation in the offspring
What is the male reproductive part of a flower called?
The stamen
What is the female reproductive part of a flower called?
The carpel
What does the stamen consist of?
The anther
The filament
What does the anther contain?
pollen grains - these produce the male gametes (sperm)
What is the filament?
The stalk that supports the anther
What does the carpel consist of?
Stigma
style
ovary
What is the stigma?
the end bit that pollen grains attach to
What is the style?
The section that supports the stigma
What does the ovary contain?
the female gametes (eggs)
What is pollination?
The transfer of pollen from an anther to a stigma, so that the male gametes can fertilise the female gametes in sexual reproduction
What is cross-pollination?
A type of sexual reproduction where pollen is transferred form the anther of one plant to the stigma of another
What do plants that cross-pollinate rely on?
insects and wind
How are plants adapted for pollination by insects?
- They have brightly coloured petals to attract insects
- They have scented flowers and nectaries to attract insects
- They make big, sticky pollen grains - stick to insects
- The stigma is also sticky - pollen stick to it
How are plants adapted for wind pollination?
- Small, dull pet as on the flower
- No nectaries or strong scents
- A lot of pollen grains - small and light to be carried by wind
- Long filaments that hang outside the flower, so a lot of pollen gets blown away
- A large, feathery stag,a to catch pollen as its carried by wind