Chapter 16- describing about concept DNA, chromosome, and gene inheritance concept

1. Chromosomes,
Genes and Proteins

2. Chromosomes: long threads of DNA inside nucleus
DNA- (deoxyribonucleic acid) molecules that carries the
codes, instruction for cells to produce the proteins needed.
Gene: part of DNA, instruction for one type of protein
Allele: Different variety of the same gene (e.g colour of
hair)

6. Humans have 46 chromosomes (23 pairs); 1 set
coming from male and female gamete
Creating the variety of charactericstics.
All humans have the genes for the same
characteristics, but different alleles combination.
*except for identical twin

7. Chromosomes in
haploid and diploid
cells
 Haploid cell: a cell with a single
set of chromosomes
 gamete cells
 Diploid cell: a cell with a pair oof
chromosomes
e.g zygote (after fertilisation)

8. Mitosis
 Cell division that produces genetically
identical cells
 For growing or repairing damaging parts of the
tissue
 Thus, produces new cells to increase body size
or replace damaged cells.
 Also used in asexual reproduction.

9. Each of the parent chromosomes are copied (duplicated).
 enough no. of chromosomes to produce new cell.
New copy remain attached to the original one.
Chromotids; two identical chromosomes
Centromere; the point where chromatids are held
together

12. Meiosis
Reduction division; the number of
chromosomes is halved for new cell.
 producing haploid cell
Human gametes are produced in the
ovaries and testes.
Haploid cell just get one
chromosome of each homologous
pair.

14. meiosis
 At the end of the meiosis, the new cells will get a
mixture of chromosome, producing a varieties of
possible genetic inheritance. (male and female
gametes)
  producing genetic variation in the offspring.

15. Mitosis vs. meiosis

16. Inheriting Genes
(Gene & Allele)
 There are variation of forms of gene for
the same characteristics;  called as
allele.
 Can be referred as letter symbols. A/a ,
B/b, C/c...
 These two genes can present in the cell
(since there are a pair of same
chromosome)
 there can be 3 possible variation of
each gene; AA, Aa, aa
 Same gene type  homozygous (AA, aa)
 Different gene type heterogenous (Aa)

17. Genotype and Phenotype
 Genotype: the gene stored inside
the chromosome
 can be AA, Aa, aa
 Phenotype: The physical
characteristics displayed/ The
features the organism has
e.g
Genotype Phenotype
AA Grey
Aa Grey
aa Charcoal

18. Dominant and
recessive allele
 Genes can have 3 combination
(genotype), but only 2 phenotype
appear
 Due to A allele is dominant to a
allele.
 Dominant allele has much effect
on the phenotype compared to
recessive allele.
  hence, recessive allele will
only show the phenotype when
there is no dominant allele

19. Codominant allele
 Some genes did not show
dominant allele over other,
 These genes can have the effect
on the phenotype 
codominance

21. ABO Blood group
(Example of
codominance )
 The ABO gene has three alleles: A,
B and O, and the blood type is
determined by the presence or
absence of these 3 alleles.
 A and B is codominant to each
other, but both A and B are
dominant to O
  produce 4 types of blood group
(phenotypes): A, B, AB and O

22. ABO Blood group
(Example of
codominance )

24. Inheritance of
genes
 Each gamete (male and
female) can only bring one
allele of each gene (haploid
cell)
 thus, will produce a lot of
variations of gene
combination in the gametes.

25. Alleles in gametes