EXTRA Flashcards
Explain what a ‘diploid cell’ is
A diploid cell has two pairs of each chromosome
Where in the cell are chromosomes found?
The nucleus
What is the diploid number for humans?
46 (23 pairs)
Describe the structure of DNA
DNA has two strands that are coiled together in a double helix.
The two strands are linked by paired bases. The 4 bases are:
- adenine
- cytosine
- guanine
- thymine
The bases always pair up in the same way (adenine + thymine // cytosine + guanine)
Explain the relationship between genes and the characteristics of an organism
Each gene codes for a specific protein, and proteins determine inherited characteristics
What is an allele?
Alleles are different different versions of the same gene, that give different versions of a characteristic. (E.g. One cat can have short fur, and the other can have long fur - from the same litter)
Describe what happens during pollination
Pollen grains from an anther are transferred to a stigma, so that male gametes can fertilise female gametes.
Define the term ‘self-pollination’
It is sexual reproduction involving the transfer of pollen from an anther to a stigma on the same plant.
Describe the process of fertilisation in plants
A pollen grain from one plant lands on the stigma of another plant. A pollen tube grows out of the pollen grain, down through the style to the ovary and into the ovule. A nucleus from the male gamete travels to the ovule to fertilise the female gamete, producing a zygote that divides to form an embryo. The fertilised female gamete forms a seed, while the ovary develops into a fruit.
Name the female sex hormone
Oestrogen
What is the function of the ovaries?
Producing ova (eggs) / sex hormones
What is the function of the Fallopian tube?
To carry the ovum (egg) from the ovary to the uterus
What is the function of the uterus?
To contain the growing embryo.
Describe the role of the placenta
To allow food, oxygen and waste substances to be exchanged between mother and fetus
Describe the role of the amniotic fluid
To protect the fetus against knocks/bumps
Are birthmarks caused by genes?
No
What is meant by the term ‘mutation’?
A rare, random change in an organism’s DNA that can be inherited
Suggest how mutations may be beneficial
A mutation could cause a gene to produce a different protein that is an improvement on the one it usually produces, which gives an organism a survival advantage.
Explain how carbon is released from dead organisms in the soil
Microorganisms decompose material from dead organisms and return carbon to the air as carbon dioxide through respiration.
Explain why fossil fuels contain carbon
Fossil fuels are formed from dead animals/plants (which contain carbon)
Explain why carbon monoxide is considered to be a pollutant
Carbon monoxide is taken in by red blood cells and prevents them from carrying oxygen, so is poisonous to humans/animals
What is the role of restriction enzymes?
Restriction enzymes effectively cut through DNA strands so that a section of DNA can be taken from a cell.
What can be used to join together different sections of DNA?
Ligase enzymes can be used to join together different sections of DNA.
When does Mitosis cell division occur?
Mitosis cell division is the type that occurs in growth, repair cloning and asexual reproduction.
