cells part two

Question 1

what is DNA and what are the four nucleotide bases and their pairs

Answer 1

deoxyribonucleic acid, A adenine - T thyamine, G guanine- C cytosine

Question 2

how many chromosomes in human genomes and how many pairs in nucleus

Answer 2

23 chromosomes, 46 in chromosome with 23 pairs, except sex cells which only have 23 chromosomes (one copy)

Question 3

what do segments of dna do on chromosomes

Answer 3

code for the production of protiens and provide the bluepirnt for each individual ‘s cell structure, body composition, features and functions.

Question 4

whats mitosis and meiosis

Answer 4

mitosis cell divsion occurs in somatic body cells. dna in nucleus is copied then the whole cell splits into twp daughter cells. putting one copy of the dna into each new daughter cell. daughter cells are identical (exact replica of parent cells) are also diploid 2n cells (contain two copies of each 23 chromosomes) . meiosis occurs in sex cells to facillitate reproduction of species. two steps meisosis 1 - parent cell divides into two daughter cells prior to this is cross over and independent assortment. meisosis 2 - daughter cells from meisos one divide into two futher duaghter cells each. since two divsion steps four daughter cells only have half amount of dna as parent cell so are hapliod n cells.

Question 5

whats RNA, its nucleotide bases and pairs

Answer 5

ribonucleic acid is the decoder and messenger for dna in the process of protein synthesis. A adenine - T thymine, U uracil - A adenine, G guanine - C cytosine. rna pairs with dna bases.

Question 6

explain protein production

Answer 6

dna codes for production of protein, codes are in sequence of nucleotide bases in dna chain. each three base sequence is called triplet, they code for specific amino acid. chain of amino acid makes protein.

Question 7

explain protein synthesis

Answer 7

1 - Dna unzips
2 - mRNA copies exposed dna, mRNA bases macth dna strand
3 - mRNA leaves nucleus, goes to ribosome
4 - mRNA moves through ribosome pairing its codons with tRNA anti codons (begins with a starter codon and finishes with a stop codon)
5 - tRNA carry amino acids and neighbouring amino acids connect to eachother

Question 8

types of rna

Answer 8

messenger rna (mRNA) - chain of rna that reads the dna by aligning itd bases with the dna bases. for each dna triplet there is a corresponding three base sequence of nucleotides in the mRNA called a codon
transfer rna (tRNA) - small units containing three rna bases called an anticodon and an amino acid. the anticodon of the trna pairs with a particular codon on mRNA

Question 9

rna codons for start and end of protein

Answer 9

AUG - start
UAA, UAG or UGA - finish

Question 10

ribosomes in cytoplasm for protein syntheisis

Answer 10

free unattached ribosomes - make soluble proteins that function in the cytoplasm
membrane bound ribosome - synthesise the protein for use within the cell membrane or outside the cell

Question 11

cell life cycle main phases

Answer 11

interphase and cell division. interphase the cell grows, produces proteins and repairs for cell divison. in cell divsion the dna and organelles of the cell are replicated and split into daughter cells.

Question 12

what are genes

Answer 12

segments of dna that code for the production of proteins. many od these proteins are enzymes that dicate the synethesis of all body molecules and how they will work together. genes are therefore expressed in the overall structure and function of individuals and in various traits eg hair colour

Question 13

explain alleles, chromosomes, heterozygous, homozygous and homologous

Answer 13

alleles - paired maternal and paternal genes which code for the same trait
chromosomes - packed genes within the cell nucleus
heterozygous - when alleles code for different expressions of a trait
homologous - maternal and paternal chromosomes paired
homozygous - when alleles code fot the same expression of a trait.

Question 14

explain dominant and recessive alleles, genotype and phenotype

Answer 14

dominant - an allele that if present will be expressed (in both homo and hetero pairs) masks the expression of recessive allele
recessive - alleles who expression only occur in homologous pairing
genotype - genetic makeup for trait based on the actual alleles present in chromosome
phenotype - is expression of genotype the actual appearence of trait eg brown hair

Question 15

describe crossing over

Answer 15

physical swapping of dna segments between a maternal sister chromatid and a paternal sister chromatid. as such each of the four chromoatids (two of each) now have a different dna sequence from one another. occurs prior to seperation during meosis 1

Question 16

describe independent assortment

Answer 16

occurs due to random alignment of sister chromatids of homologous chromosomes (forming tetrads) and their subsequent seperation during meiosis 1 followed by seperation of suster chromatids during meosis 2. independent assortment is prior to cell divison during meosis one

Question 17

explain random fertilisation

Answer 17

completely random which sperm will fertilize which egg

Question 18

explain simple and complex inheritance

Answer 18

simple - a single gene pair codes for a particular trait
complex - mutilple gene pairs code for a particular trait. the different gene pairs may exist on the same or different chromosomes and work in tandem to dictate particular traits

Question 19

explain dominant recessive inheritence and incomplete dominance

Answer 19

domiant recessive - domiannt alleles are always expressed if present and recessive alleles are only expressed if they exist in homologous pairs
incomplete dominance - a heterozygous genotype that expresseds an intermediate phenotype eg having both recessive and dominant phenotype expressed.

Question 20

explain multiple allele inheritence and co dominance

Answer 20

multiple allele - when a gene has more than two allele types
co dominance - when two or more of those alleles are dominant eg blood types