B16 - chromosomes & genes, cell division, monohybrid inheritance Flashcards
which cell has no nucleus
red blood cells
which cells are haploid
gametes
which cells are diploid
all body cells except gametes & red blood cells
how many chromo. & sets in haploid in humans
n = 23
(n = a set of chromo.)
how many chromo. & sets in diploid in humans
2n = 46
-23 pairs
(n = a set of chromo.)
note: no. chromo. varies depending on organisms
how do you number the human chromo.
-largest pair is 1st
-last pair is 23rd pair (sex chromo.)
how long is DNA in each nucleus
2m
what is 1 chromo. to DNA
-1 chromo. = 1 DNA molecule
note: nucleus - chromosome - gene - allele - DNA - bases
how many bases code 1 amino acid
every 3
define inheritance
transmission of genetic information from generation to generation
eg. eye colour, hair colour, height
define chromosome
-made of DNA which contains genetic info in the form of genes
eg.
-46 chromo. (23 pairs) in every nucleus - 23 from sperm, 23 from egg
-arranged in pairs
define gene
-a length of DNA that codes for a protein
-eg. brown eyed protein
define Allele
-an alternative version of a gene
-eg. brown eyed allele
define haploid nucleus
-nucleus containing a single set of chromo.
eg. gametes, pollen & ovaries
define diploid nucleus
-nucleus containing 2 sets of chromo.
eg. in all body cells (2n = 46 [in pairs])
define gametes
sex cells ( sperm & egg)
define zygote
-fertilized egg
how to make a zygote
-sperm + egg -> zygote
- 23 chromo. [n] + 23 chromo. [n] -> 46 chromo [2n]
23rd chromo. of males & females
-male = XY
-female = XX
chromo. of egg
X, X
chromo. of sprem
X, Y
-50% - X, 50% - Y
% of gender out come as girl/ boy
50%
define mitosis
-nuclear division giving rise to genetically identical cells
(diploid -> diploid)
note: mitosis happens after DNA replication
2n - 2n - (mitosis) n
where does mitosis happen
-in all body cells except red blood cells & gametes
how does mitosis happen
-DNA replicates = 2 copied of 46 chromo.
-cell divides
-each copy in a daughter cell
how many daughter cells in mitosis
2
roles of mitosis for humans
-growth
-repair of damaged tissues
-replacement of cells
roles for mitosis for humans and animals
-growth
-repair of damaged tissues
-replacement of cells
-asexual reproduction
how are daughter cells in mitosis to each other & parent cell
genetically identical to each other & parent cell
what do you call the cell before it divides
parent cell
define meiosis
reduction division in which the chromo. no. is halving from diploid to haploid resulting in genetically diff. cells
(need for sexual reproduction)
(haploid-> diploid -> haploid)
where does meiosis happen
-ovaries & testicles
how does meiosis happen
-DNA replicates = 2 copies of 23 chromo.
-chromo. pairs pair up and sections of DNA is swapped randomly- so genetically diff.
-first division = chromo in pairs are separated & cell divides
-second division = no DNA replication, chromo. pairs are separated- only chromo. now, cell divides
how many daughter cells in meiosis
4
roles of meiosis
-reduction division: diploid -> haploid
-genetic variation (genetically diff. daughter cells)
-making gametes
how many division in mitosis & meiosis
-mitosis = 1
-meiosis = 2
how are daughter cells in meiosis to each other & parent cell
genetically diff. to each other & parent cell
where is chromo. found in cells
nucleus
define genotype
genetic make up of an organism in terms of an allele present
(always in 2 symbols)
eg, BB, Bb, bb
define phenotype
observable features of an organism
(always in words)
eg, brown eyes, blue eyes, curly hair
define homozygous
having 2 identical alleles of a particular gene
eg, BB, bb
define heterozygous
having 2 alleles of a particular gene
eg, Bb
define pure bred
2 identical homozygous individuals breed tgt
eg, BB & BB, bb & bb
define not pure bred
2 heterozygous individuals will not pure breed
define dominant allele
allele that is expressed if it is in the genotype
(always first letter & capital)
define recessive allele
allele only expressed when there is no dominant allele in the gene
(always small letter)
another name for punnett squares
genetic diagram
which genotype is parental cross btw
eg, RR x rr
homozygous dominant & recessive
phenotype ratios for dominant to recessive in parental cross
1: 0
100% dominant allele in all
which genotype is F1 cross btw
eg, Rr x Rr
heterozygous dominant
phenotype ratios for dominant to recessive in F1 cross
3: 1
75% dominant allele in all
which genotype is test cross btw
eg, Rr x rr
heterozygous dominant & homozygous recessive
phenotype ratios for dominant to recessive in test cross
1: 1
50% dominant allele in all
how many alleles do gamete have
1
how many alleles do genotype have
2
where does mitosis happen in plants, say 1
ovary
where does mitosis happen in animals, say 1
testis
why is mitosis important for gametes
maintains diploid number on fertilisation
