This document defines key terms related to inheritance and genetics. It explains that chromosomes carry DNA and genes, which code for traits and proteins. DNA is made of nucleotides with nitrogenous bases that form base pairs. Genes on chromosomes can have different alleles that are transmitted from parents to offspring. The genetic code in DNA is transcribed into mRNA and translated into proteins using triplets of bases called codons that specify amino acids.

1. INHERITANCE
by Miss Nadia Khamshah

2. 17.1 Inheritance
Retrieved from syllabus
2020/2021

3. Inheritance
The transmission of genetic
information from one generation to
the next,
leading to continuity of the species
and variation within it.

4. 17.2 Chromosomes, genes and protein
Retrieved from syllabus
2020/2021

5. Chromosomes
Is a thread-like structure of DNA, carrying genetic
information in the form of genes
Gene
Is a length of DNA on a specific locus on a
chromosomes that codes for protein
Locus
Is a specific, fixed position on a chromosome
where a particular gene is located

6. Characteristic
Is a heritable feature such as height, eye color, blood group,
presence of dimples
Trait
Is a variation of a specific characteristic (tall/drawft)
Allele
Alternative form/version of a gene of a specific
traits (represent by letters: T/t)

7. Phenotype
Is the observable characteristic of organism (tall/drawft)
Genotype
Is the genetic composition of an organism that cannot
be seen (TT/Tt/tt)
Dominant allele
An allele which always shows its trait when it is present,
suppress recessive allele. Represented by capital letter, T

8. Recessive allele
An allele which shows its traits when both alleles are recessive
allele, suppressed by dominant allele. Represented by small
letter, t
Dominant trait
Is expressed when both alleles are dominant alleles or one
dominant allele is paired with recessive allele, TT/Tt
Recessive trait
Is expressed if a recessive allele is paired with another
recessive allele, tt

9. Homozygotes
Both allele at loci of a pair of homologous chromosomes are
the same, TT/tt
Heterozygotes
Allele at loci of a pair of homologous chromosomes are
different, Tt
Purebreed
Individual which carries two identical alleles for a trait. Self cross
always produce offspring with same characteristics

10. Parental generation
Refers to the first generation of two individuals which are
mated to predict or analyse genotypes of their offspring
Filial generation
Refers to a successive generation as a result of mating
between individuals of purebred parental generation

12. Key
definitions

13. Chromosomes, DNA, genes and alleles
In the nucleus of every cell there are a number of long threads called chromosomes.

15. Chromosomes
Chromosomes are a packaged form of DNA. The DNA
normally exists in a non-condensed form in the cell
nucleus.
It condenses into chromosomes during cell replication.

16. • A human body cell (somatic cell) nucleus contains 46 chromosomes.
• Exists in pairs, hence 23 pairs (23x2=46 chromosomes)
• There are two types of chromosomes, autosome and sex
chromosomes
• Human somatic cell consists of 44 autosomes and 2 sex
chromosomes
Chromosomes

17. Comparison
Type of chromosomes Autosome Sex chromosome
Feature Consists of
chromosome pairs
from number 1 to 22
Consists of one
chromosome pair, that
is number 23
Function Controls all
characteristics of
somatic cells
Consists of genes
which determine
gender
Example Blood groups, height,
skin colour
Male: XY
Female: XX

19. Karyotype
• The number and structure of chromosomes present in a cell nucleus
• Chromosomes are arranged in pairs, based on homologous
chromosomes in terms of their sizes, centromere location and
banding pattern

21. Let’s analyse and describe
the human karyotype
[revision from topic Variation]

26. Somatic cell
• A somatic cell is all cell in the
body except reproductive cell
(sperm and egg cells).
• Somatic cells are diploid,
meaning that they contain two
sets of chromosomes, one
inherited from each parent.

27. Sex cell
• Also known as reproductive cell or gamete
• Ova – female gamete
• Sperm – male gamete
• Haploid, half the number of normal
chromosomes. Through a process called
Meiosis
• Hence, each gamete contains 23
chromosomes (1 pair)

28. Inheritance of sex in humans
Of the 23 pairs of chromosomes present is each
human cell, one pair is the sex chromosomes.
These determine the sex of the individual.
Male have XY, female have XX.
So the presence of a Y chromosome results in male
features developing.

29. HOW YOU CAN BE A GIRL OR A BOY?

30. Haploid and Diploid

32. Gene
Each chromosome is made up
of a large number
of genes coding for the
formation of different proteins
which give us our
characteristics.
The gene responsible for a
particular characteristic is
always on the same relative
position on the chromosome.
A part of a DNA molecule coding for one protein is
called a gene.

33. Alleles
When the chromosomes are in pairs, there may be a different
form (allele) of the gene on each chromosome.

35. The Genetic Code

36. The genetic code
Retrieved from syllabus
2020/2021

37. DNA
Each chromosome contains one very long
molecule of DNA.
The DNA molecule carries a code that instructs
the cell about which kind of proteins it should
make.
Each chromosome carries instructions for
making many different proteins.

38. DNA
•DNA are polymers made of long chains of
nucleotides.
•A nucleotide consists of:
•a sugar molecule
•a phosphate group
•a nitrogen-containing base

41. Nucleotide structure of DNA

42. Double helix DNA
First strand Second strand

43. Nitrogenous bases
DNA RNA
adenine (A) adenine (A)
cytosine (C) cytosine (C)
guanine (G) guanine (G)
thymine (T) uracil (U)
WE WILL LOOK AT THIS LATER
WE WILL LEARN THIS FIRST

44. Differences between DNA and RNA

45. DNA
COMPLEMENTARY BASES
Adenine
Adenine
Thymine
Cytosine
Guanine
Thymine
Cytosine
Guanine

48. How protein is made
Retrieved from syllabus
2020/2021

49. Gene
Each chromosome is made up
of a large number
of genes coding for the
formation of different proteins
which give us our
characteristics.
The gene responsible for a
particular characteristic is
always on the same relative
position on the chromosome.
A part of a DNA molecule coding for one protein is
called a gene.

52. RNA
STRAND
Adenine
Adenine
Thymine
Cytosine
Guanine
Uracil
Cytosine
Guanine
DNA
STRAND
Transcription

53. PLEASE TRANSCRIPT THIS TO RNA
Use this strand as template

54. A-U-G-A-U-C-U-C-G-U-A-A
RNA STRAND
(mRNA)
TRANSCRIPTION
DNA TEMPLATE STRAND

55. How do they TRANSLATE the message?
(Translation)
Three bases = one amino acid
Example:
C-G-A = Alanine
A-U-G = Methionine
TRIPLET
CODON
AMINO ACID
(monomer for
protein)

56. A-U-G-A-U-C-U-C-G-U-A-A
RNA STRAND
(mRNA)
TRANSLATION
DNA TEMPLATE STRAND
TRIPLET
CODON

59. EXERCISE
A-T-G-C-C-G-C-A-A-T-C-T-G-T-T-C-A-G
T-A-C-G-G-C-G-T-T-A-G-A-C-A-A-G-T-C
DNA STRAND
PLEASE WRITE DOWN THE COMPLEMENTARY DNA STRAND FOR THE
FIRST STRAND GIVEN.

60. TRANCRIPTION
T-A-C-G-G-C-G-T-T-A-G-A-C-A-A-G-T-C
DNA TEMPLATE STRAND
PLEASE TRANSCRIPT THE DNA TEMPLATE GIVEN
A-U-G-C-C-G-C-A-A-U-C-U-G-U-U-C-A-G
mRNA STRAND

61. TRANSLATION
A-U-G-C-C-G-C-A-A-U-C-U-G-U-U-C-A-G
mRNA STRAND
MET- PRO – GLU – SER – VAL - GLU

66. THANK YOU
References:
• Hodder Biology
• KSSM Biology Form 5