4.6 Reproduction TRIPLE Flashcards
A cell divides in a series of stages called
the cell cycle
What are the initial steps in the cell cycle?
The cell grows and organelle numbers increase, DNA replicates.
In the cell cycle after the DNA has replicated what happens next?
The copied chromosomes separate (mitosis) and then the cell divides into two.
What are the 2 forms of reproduction?
Asexual and sexual
Why is asexual reproduction important?
growth and repair
How many parents are involved in asexual reproduction?
1
How many parents are involved in sexual reproduction?
2
Which form of reproduction involves gametes?
sexual - fusion of egg and sperm
Which form of reproduction brings about variation?
sexual
Name an organism that reproduces asexually
bacteria, daffodil bulbs, strawberry tubers
Name an organism what reproduces sexually
humans
What form of cell division produces gametes?
Meiosis
Where does meiosis occur?
testes and ovaries
Where does mitosis occur?
in all body cells except testes and ovaries
In plants what are the sex cells?
pollen and egg cell
In animals what are the sex cells?
egg cell and sperm
What is another name for a gamete?
sex cell
Why does sexual reproduction bring about variation
Involves FUSION of egg and sperm, creating a unique combination of alleles
Give an advantage of sexual reproduction
produces variation in offspring giving it a survival advantage if the environment changes
Give a disadvantage of sexual reproduction
need 2 parents, more energy is needed, slower process and fewer offspring produced
Give an advantage of asexual reproduction
Only need one parent, less energy is needed (more energy efficient), faster than sexual reproduction
Give a disadvantage of asexual reproduction
No variation, therefore susceptible to environmental changes
How many chromosome pairs are found in human body cells?
23 pairs
How many chromosomes are found in human sex cells
23
Chromosomes are found
in the nucleus
Chromosomes are made up from
DNA
Put the following in order of size starting with the smallest
cell, gene, nucleus, chromosome
gene, chromosome, nucleus, cell
What are genes?
Short sections on DNA found on chromosomes - they code for a particular characteristic
How are mitosis and meiosis different?
Mitosis is used for growth and repair, meiosis makes gametes
How many times does the cell divide in meiosis?
twice
How are the cells produced different from the parent cell in meiosis
they have half the chromosome number
How many cells are produced at the end of meiosis?
4
How many cells are produced at the end of mitosis?
2
At fertilisation what happens to the chromosome number?
It doubles and chromosome number is restored.
In the first step in meiosis what has to happen?
DNA/chromosomes copy/replicate themselves
Are the cells produced at the end of meiosis genetically identical or genetically different?
genetically different
During fertilisation what happens?
egg and sperm cell fuse together
Following fertilisation, what cell is made?
Zygote (fertilised egg)
What happens to the the fertilsed egg made following fertilisation?
It will divide by mitosis, cell number will increase to form an embryo and then eventually a foetus
What makes an embyro and a foetus different?
A embryo contains unspecialised cells, a foetus contains cells that have begun to specialise - they have differentiated.
What does differentiation mean?
When cells (in an embryo) begin to specialise
Give an example of a specialised cell
muscle, red blood cell, nerve
What is the genome?
It describes all of the genetic material that an organism has
Describe the structure of DNA
Double helix
Where is your DNA found?
In the nucleus in the form of chromosomes
How are genes and proteins linked together?
genes (code for characteristics) code for a sequence of amino acids that make a protein
Why is studying the genome important?
Search and study genes that cause disease, then try and treat the disease
TRIPLE DNA is a polymer made from 4 different nucleotides - what are nucleotides made from?
base, sugar and phosphate
TRIPLE Name the bases found in DNA
A, T, G and C
TRIPLE Which bases pair together?
AT and GC
TRIPLE How do the bases code particular amino acid sequence?
Sequence of bases grouped into 3s, every 3 bases codes for a specific amino acid
TRIPLE What do the order of the bases in DNA detemermine?
The order of the amino acids that make up the protein
TRIPLE In a long DNA molecule how are the sugar and phosphate arranged?
alternating
TRIPLE Which part of the nucleotide is the base attached to?
the sugar
A DNA polymer is made up of…
repeating nucleotide units/monomers
Define phenotype
outward appearance
define genotype
combination of alleles
Where are proteins synthesised?
ribosomes
TRIPLE When a protein in synthesised using DNA what carries the message to the ribosomes
template - mRNA
TRIPLE what molecule brings in specific amino acids according to the template to make a protein?
carrier molecules (tRNA)
TRIPLE When protein synthesis is complete what happens to the synthesised protein?
It folds up into a unique shape
What types of jobs can proteins have?
enzymes, hormones, structural proteins e.g. collagen
TRIPLE What is a mutation?
A change in the base sequence of DNA
TRIPLE what effect can mutations in DNA have on proteins?
Some may have no effect, others may completely alter the protein e.g. an enzyme no longer fits its substrate
TRIPLE Which parts of the DNA molecule DO NOT code for proteins?
Non-coding sections
TRIPLE What role can these non-coding portions have?
They can switch genes on or off
Of the 23 pairs of chromosomes in a body cell, how many control characteristics only?
22
The 23 rd pair of chromosomes is called the sex chromosomes, what they in females and males?
females - XX
males XY
Name a genetic disorder that is inherited
cystic fibrosis or polydactyl
What is polydactyl?
Having extra digits
What is polydactyl caused by?
A dominant allele
What is cystic fibrosis?
A disorder of the cell membranes
What is cystic fibrosis caused by?
A recessive allele
Name characteristic caused by a SINGLE gene
tongue rolling, attached ear lobes
Name characteristics caused by MULTIPLE genes
eye colour, hair colour, height, nose shape
What is a dominant allele?
where only one copy of the allele is required to express that trait -this allele is always expressed if present
What is a recessive allele?
where two copies are required to express that trait, its not expressed in presence of a dominant allele
What does homozygous mean?
Where you have two copies of the SAME allele for a given characteristic e.g. BB, bb
What does heterozygous mean?
Where you have 2 different copies of an allele for a given characteristic e.g. Bb
What is an allele?
A different version of the same gene e.g. blue eyed allele, green eyed allele, brown eyed allele
What are enzymes?
Proteins that are biological catalysts
What are hormones?
Chemical messengers that travel in the blood stream to a target organ
TRIPLE: What is mRNA
a molecule that carries the DNA code to the ribosomes from the nucleus
TRIPLE: When do mutations occur
randomly
TRIPLE: When can mutation rate be increased?
exposure to UV, chemical carcinogens, radiation
TRIPLE: A mutation changes the DNA base sequence of a gene - what does this create?
a different version of the gene - a new allele
TRIPLE: Give some examples of mutations
insertion, deletion and substitution
Do gametes have one or two copies of each chromosome?
one
What are the chances of have a pregnant lady have a boy?
50%
What sex chromosome do you find in a sperm?
X or a Y
What sex chromosome do you find in an egg cell?
X only
What sex determines the sex of the child?
Father - you will always receive an X from mum and then X OR Y from dad
How could you determine whether a pregnant woman was carrying a child with a genetic disorder?
embryo screening
Why might people be against embryo screening?
its expensive, may lead to designer babies and all parents wanting to screen embryos and pick the most desirable
Why are people for embryo screening?
stops suffering
treating disorders can be expensive
there are laws to stop it going too far
