DNA Flashcards
(28 cards)
What two types of reproduction are there?
Asexual reproduction and sexual reproduction
What is the difference between sexual and asexual reproduction?
asexual reproduction only involves one parent whereas sexual reproduction involves the fusion of a male sex cell and a female sex cell (gametes) from two parents to form a zygote
there is genetic variation in the offspring created by sexual reproduction whereas the offspring produced by asexual reproduction are genetically identical to the parent cell (clones)
asexual reproduction is usually faster than sexual reproduction as it doesn’t involve meiosis (the creation of gametes) or fertilisation and only requires one parent
What are the gametes involved in sexual reproduction in plants?
egg cells
pollen
What are the gametes involved in sexual reproduction in animals?
sperm cells
egg cells (ova)
What is the importance of mitosis?
growth of multicellular organisms: zygotes divide rapidly to form an embryo made up of cells with the same genetic material
replacement of cells and repair of tissues
asexual reproduction
What is cell division in sexual reproduction called?
meiosis
What is the acronym to describe the processes occurring in mitosis and meiosis?
Interphase
Prophase
Metaphase
Anaphase
Telophase
What occurs in interphase for both mitosis and meiosis?
Interphase- DNA replication: chromosomes doubled (while they still have 46 chromosomes, there are two chromatids called sister chromatids)
What occurs in prophase 1?
Prophase 1: mother’s pair joins up with father’s pair of chromatids forming a group of two chromosomes (homologous chromosomes)
-one chromatid from each pair gets entangled with corresponding chromatid from other side (crossing over)
How does genetic variation occur in Prophase 1 in meiosis?
when crossing over, two chromatids swap certain sections of DNA (recombination)
What occurs in metaphase and anaphase 1?
chromosomes line up in middle of cell and during anaphase, the spindle fibres pull the two chromosomes to opposite ends
what occurs in telophase 1?
chromosomes arrive at opposite poles of the cell
the cell pinches apart in the middle through cytokinesis
nuclear membrane reforms around 2 new daughter cells
How do gametes end up with half the number of chromosomes as their parent cell?
DNA replication doesn’t occur in meiosis II therefore, two sister chromatids split per daughter cell instead of the pair of homologous chromosomes in meiosis I resulting in the creation of 4 haploid cells containing a single copy of each chromosome
What is a haploid cell?
contains one complete set of chromosomes
What happens during fertilisation?
gametes fuse to produce a single new body cell with 23 pairs of chromosomes (46)
What is natural selection and how does sexual reproduction benefit this?
due to the recombination of chromosomes in prophase I, meiosis produces genetically varied gametes through the mixing of genetic material which produces different combinations of alleles. Through this, if the environment changes, variation gives a survival advantage as some offspring will be able to survive and reproduce.
What are chromosomes?
long molecules of DNA
What is DNA?
a polymer, long molecule, made up of many repeating units
Can you describe the structure of DNA?
two strands which twist together to form a double helix
What are genes and what do they do?
Genes are small sections of DNA which code for a particular sequence of amino acids to make a specific protein.
What is DNA made up of?
nucleotides
What three parts do nucleotides consist of?
deoxyribose sugar
a phosphate
nitrogenous base
How does the order of bases along the DNA double helix affect genetic variation?
the order of bases determines the order in which amino acids are assembled to build proteins; this is called the genetic code
What four bases are there?
adenine (A), thymine (T), cytosine (C), and guanine (G)
