B13(Reproduction) Flashcards
What is asexual reproduction
-There is no fusion of gametes and only parent
-there is no mixing of of genetic information, leading to genetically identical offspring
What is sexual reproduction
-Involves the fusion of male and female gametes formed by meiosis
-there is a mixing of genetic information that leads to variation in the offspring
What is mitosis
Cell division resulting in 2 identical cells with exact copies of all the chromosomes
What is meiosis
A special form of cell division resulting in 4 differing sex cells being formed
What is fertilisation
When 2 sex cells join and dna forms a single nucleus
What are the advantages of asexual reproduction
Quicker, many identical offspring, lower risk, no need to find mate,lower energy requirement
What is a disadvantage of asexual reproduction
No variation
What are the advantages of sexual reproduction
-More variation in offspring
-this variation gives a survival advantage if environment changes
What are the disadvantages of sexual reproduction
-much more risky
-relies on 2 cells fusing
-time and energy is used to find a mate
-greater energy requirement
What is a haploid
Cells containing one version of each chromosome
What is a diploid
Cells containing pairs of chromosomes
What is a zygote
When gametes fuse
What is DNA
-The genetic material in the nucleus of a cell
-2 long strands wound together in a double helix
What are base pairs
-Pairs of bases held together by hydrogen bonds
-3 pairs gives the code for an amino acid
What are the 4 bases
A
T
C
G
What are the pairs of the bases
A and T
C and G
What is a gene
-A specific section of DNA on a chromosome
-code for a specific sequence of amino acids
What are chromosomes
Long chains of DNA that contain thousands of genes joined together
What are nucleotides made from
-phosphate group
-ribose sugar
-nitrogenous base
What is the process to make proteins
-DNA in the nucleus is used to produce a template
-The template leaves the nucleus and binds to a ribosome
-carrier molecules bring specific amino acids and attach themselves to the template
-The amino acids join together to make a protein
-Repeats step 3 and 4 until the entire protein chain is assembled
-protein detaches and the carrier molecules collect more amino acids
-protein then folds up to its specific shape
What are mutations
changes in the sequence of bases in a strand of DNA
What is an Allele
Different versions of the same gene
What does heterozygous mean
-The 2 alleles are different
-for example a person can have a blue eye allele and one brown eye allele
What does homozygous mean
-The 2 alleles are the same
-for example a person can have 2 blue eye alleles
What is a genotype
Tells us which alleles a person has for a particular gene
-for example a person has 2 copies of the blue eyes allele so has a genotype of bb(blue)
What is a phenotype
The characteristic that is caused by a particular genotype
What is a dominant allele
-always expressed in the phenotype even if only one copy is present
What is a recessive allele
-only expressed if 2 copies are present
How is sex inherited
23 pairs of chromosomes, 22 control body characteristics but only one pair carries the gene that determines sex
What are the sex chromosomes in females
XX
What are the sex chromosomes in males
XY
What is chorionic villus sampling
-carried out on embryonic cells between10-12 weeks
-by taking a small sample of tissue from the developing placenta
What is Amniocentesis
-carried out on the foetus between 15-16 weeks
-involves taking fluid from around the foetus
-this fluid contains cells used for screening
