Biology Lecture 7 DNMU

1. PATTERNS
OF
INHERITANCE

2. PLAN OF LECTURE
1. GENETICS and HUMAN GENETICS
2. MAIN CONCEPTS of GENETICS
3. MENDEL'S LAWS of INHERITANCE
4. MONOGENOUS DISEASES
5. MENDELIAN TRAITS IN HUMANS

3. STUDENTS' INDEPENDENT STUDY PROGRAM
Objectives for Students' Independent Studies
1. General genetics and human genetics as sciences.
2. The main terms of genetic.
3. The classification of cross: monohybrid, dihybrid,
polyhybrid and test cross.
4. Patterns of inheritance.
5. Mendel's Laws of inheritance
6. Mendelian Traits in humans.
7. Monogenous diseases.
Applicable literature materials:
Medical biology / K. L. Lasarev – Simferopol: IAD
CSMU, 2002. p. 114 - 123.

4. KEY WORDS AND PHRASES:
GENETIC, ANTHROPOGENETIC, HEREDITY,
INHERITANCE, GENE, GENOTYPE, PHENOTYPE,
GENOME, ALLELE, LOCUS, HETEROZYGOUS,
HOMOZYGOUS, GENETIC ANALYSIS, DOMINANT
CHARACTER, RECESSIVE CHARACTER,
MONOHYBRID CROSS, POLYHYBRID CROSS, TEST
CROSS, MENDELIAN TRAITS, MONOGENOUS
DISEASES.

5. • Genetics is the science that learns
the peculiarities of the hereditary
and variability, which are the main
characteristics of living things.
• Human genetics (anthropogenetic)
is the science that learns the
peculiarities of hereditary and
variability in human organism.

6. 2. MAIN CONCEPTS of GENETICS
• Heredity - is the transmission of
characteristics from parent to
offspring through the gametes.
• Gene - a unit of heredity, a segment
of a DNA that contains all the
information required for synthesis of
polypeptide chain. Each gene has a
specific position (locus) on a
chromosome.

8. Allele
- an alternate form of a gene, that
can occupy a particular
chromosomal locus. In humans and
other diploid organism there are
two alleles, one on each
chromosome of a homologous pair.

10. An individual who has two
identical alleles for a gene at a
particular locus on homologous
chromosomes is homozygous for that
gene.
An individual with two different
alleles at a particular locus on
homologous chromosomes is
heterozygous.

12. INHERITANCE - is the way of passing of
hereditary information, which depends on
the forms of reproduction.
During asexual reproduction the main
traits are inherited through spores or
vegetative cells, that's why the maternal
and daughter cells are very similar.
During sexual reproduction the main
traits are inherited through gametes.

13. • Genotype- is the genetic constitution of an
organism (a diploid set of genes).
• The genotype describes the organism's
alleles, whole the phenotype describes the
outward expression (physical appearance of
an individual) of an allele combination.
• The phenotype of an individual is the
observable outward manifestation of the
genes that it carries.
• Genome - is a collection of genes of an
organism in cells (may be a haploid set of
genes).

16. THE GENERAL GENETIC SYMBOLS OF
SOLVING THE SITUATIONAL TASKS:
1) By Latin letters (А, а)mark alleles
genes, which reply to alternative traits
(signs).
2) The parent generation is called as
"P".
3) Female genotype is written first and
has the symbol (the mirror of
Venus, the godess of beauty);

17. 4) the male genotype the symbol ♂ is
used (the shield and the spear of Mars
- god of war).
5) The interbreeding is marked by the
sign of multiplication (x).
6)The offsprings are called as letter F
(Lat. filii) with numeral index, which
belongs to number of the generation
( F1 - children, F2 -grandchildren, etc.)

18. MONOHYBRID CROSSES
P
F1
F2
parents
f i l i i
f i l i i
АА аа

19. THE CROSSES THAT INVOLVE ONLY ONE
TRAIT (ONLY ONE PAIR ALLELES) ARE
CALLED MONOHYBRID CROSSES.
THE CROSS BETWEEN INDIVIDUALS, WHICH
DIFFER IN TWO VARIOUS TRAITS (TWO PAIRS
ALLELES) ARE CALLED DYHYBRID CROSSES (TWO
PAIRS GENES IN TWO PAIRS OF CHROMOSOMES
- NOT LINKED INHERITANCE).

22. 3. MENDEL'S LAWS of INHERITANCE
I. The law of monotony of the first
filial generation:
DURING CROSSING TWO HOMOZYGOUS
WHICH ARE DIFFER FROM EACH OTHER BY ONE
TRAIT ALL PROGENY IN THE FIRST FILIAL
GENERATION IS MONOTONY AS WELL AS
PHENOTYPIC AND GENOTYPIC.

23. LAW OF MONOTONY
P parents
F1
AAaa
Aa
G: Aa
♂

25. II. THE LAW OF SEGREGATION:
STATES THAT FROM A PAIR OF CONTRASTING
CHARACTERS (ALLELES) ONLY ONE IS PRESENT
IN A SINGLE GAMETE AND IN F2 THESE
CHARACTERS ARE SEGREGATED IN THE RATIO
OF THREE TO ONE (3:1) BY PHENOTYPE
AND 1:2:1 BY GENOTYPE.

26. LAW OF SEGREGATION
P
G:
F2
3 : 1
parents
Aa Aa
A, aA, a
AA Aa aaAa
♂

29. III. LAW OF INDEPENDENT ASSORTMENT
Based upon the results of the dihybrid
cross, Mendel proposed what is now
know as
THE LAW OF INDEPENDENT ASSORTMENT,
WHICH STATES THAT A GENE FOR ONE TRAIT
DOES NOT INFLUENCE THE TRANSMISSION OF
A GENE FOR ANOTHER TRAIT.

32. This is the classic dihybrid ratio, which indicates that
both parent are heterozygous at both loci.

33. This ratio is the result of the two genes behaving completely
independently of each other in the cross (not-linked inheritance).

35. MENDELIAN TRAITS in HUMANS
MENDEL'S LAWS APPLY TO ALL DIPLOID
SPECIES.
THE NATURE OF THE PHENOTYPE IS
IMPORTANT WHEN-EVALUATING
TRANSMISSION OF MENDELIAN TRAITS.
IN HUMANS, DISORDERS OR TRAITS CAUSED
BY A SINGLE GENE ARE CALLED MENDELIAN
TRAITS.

36. MENDELIAN TRAITS in HUMANS

38. • Brachydactyly - Short fingers.
• Polydactyly - Extra fingers and
toes.
• Huntington's disease -
Degradation of nervous system,
starting in middle age.
SOME DOMINANT TRAITS IN HUMANS:

39. Brachydactyly
Polydactyly

40. Huntington's
disease

45. SOME RECESSIVE TRAITS IN HUMANS:
• Albinism - Lack of melanin
pigmentation.
• Alkaptonuria - Inability to
metabolize homogenic acid.
• Duchenne muscular dystrophy
- Wasting away of muscles during
childhood.

46. Albinism
- Lack of
melanin
pigmen-
tation.

49. Alkaptonuria
- Inability to
metabolize
homogenic
acid

51. Duchenne
muscular
dystrophy