Categories
Biology

Genetics – Character or trait

Genetic is the study of heredity and variation in living things

HEREDITY OR INHERITANCE  is defined as the   transmission and expression of characteristics or traits

in an organism from parents to offspring.

VARIATION  is  defined as the differences which exists between parents and offspring as well as a  many  the offsprings.

CHARACTERS OR TRAIT THAT CAN BE TRANSMITTED IN MAN

It is only those traits that  constitute the genetic makeup of the parents that can be transmitted and expressed in the offspring.

These traits include colour of the skin, colour of eyes this colour of the hairs and hair texture, size  of body stature, shape of the head , shape of the ears,  shape of the month,  lips, shape of the nose, length  of the         hands and legs,length of neck ,  Blood grouping,      baldness, tongue rolling,  hemophilia        , voice,  intelligences composure, aptitude  , sickle cell anaemia are transmissible in animals while is transmissible include  colour and shape of the leaves shoot , seed size and shape, colour of the flowers,        size of the fruit and pigmentation

HOW CHARACTERS OR TRAITS GET TRANSMITTED FROM GENERATION TO GENERATION

Only characters controlled by genes can be transmitted A diploid organisms has two sets of chromosome referred  to as homologues. Such an organism has two copies of each gene, with each  copy occupying identical locations or  loci on the homologous chromosomes.

Diploid organisms produce gametes by   meiosis in their reproductive organs  . A  male individual produces egg cells or ova.. During meiosis the number of chromosome in  a cell is halved , the gametes are therefore haploid containing one set of chromosome  and gene only one copy of each gene.

During sexual reproduction, the gamete of a male and female individual  fuse to form zygote. Each zygote is diploid as it gets one set of chromosomes, and hence one copy of each gene from the gametes of each parent. The gene an organism inherits during fertilization is called genotype remain constant throughout life span. The phenotype which is the physical appearance or features of an organism is determined by its genotypes and the environment in which it lives.

Basic Genetic concepts

GENE; This is defined as the physical unit of inheritance transmitted from due generation another and responsible for controlling the development of characters in the new organisms.

CHROMOSOMES: these are strands of genetic materials which are obvious during cell division. They are found in the nucleus where they carry the genes. They contain of DNA (deoxyribonucleic acid) and protein.

CHARACTER OR TRAIT:

These are inheritable attributes or features possessed by an organism’s height or size.

ALLELOMORPHS these are pairs of genes or locus that controls contrasting character.  Pair of allomorphs are called allelic pair while each member of the pair is the allele of the other.

PHENOTYPE: Is the sum total of all observable features of an organism s that is the physical, physical, physiological and behavioral traits e.g. height, weight, skin colour.

GENOTYPE; The term in used to describe those traits or sum total of the genes inherited from both parent or in order word, it is the genetic makeup  or  constitution  of an individual. Genotype includes both the dominant and the recessive traits that form the genetic  makeup of an individual.

DOMINANT charater;This is a trait that is expressed in an offspring when two individual with contrasting characters are crossed.

RECESSIVE: Character this is the trait from one parent which is masked or does not produce its effect in the presence of dominant gene or character. Shortnees is recessive character while fellness is dominant character. Recessive genes are gene which control recessive character,

HOMOZYGOUS: Is  an individual with  identical alleles in respect of a particular trait or character (TT or  tt).

HETEROZYGOUS: An individual having  two member of a pair of genes controlling  a pair of contrasting alleles located on different on the same position on a pair of chromosome  e.g.  (Tt  for  tallness or  a plant with  Rr.

GAMETE – Is a single cell formed as a result of the union of a ale gamete with a female gamete

FILIAL  -Generation  – the offspring of parent make up the filial generation the first, second and third generations of offspring are known as first, second  and third filial generations   of offspring are known as first, second and third filial generation are denoted by the symbols F1, F2 and F3.

HYBRID: Is an offspring from a cross between parents that are generically different parents that are generically different but of the same species.

HYBRIDIZATION – is the crossing of a plant with contrasting character.

MONOHYBRIDIZATION: Involves the crossing of two organisms with two organisms with two pairs of contrasting character.

LOCUS- is the site for location of gene in a chromosome.

HAPLOLD- Is when  an organism has one set of chromosomes in the same genete it is represented by (n).

DIPLOID– Is when an organism has two sets of chromosomes in the body cell. The bodies of animals and plants are diploid. Diploid number is represented by (2n).

MUTATION – Is a change in the genetic makeup of an organism that resulting in a new characteristic that is inheritable

BACKCROSS –  This is the  mating of an f1  individual with an individual which has the parental genotype.

PURE BREED    – This simply means an individual that is homozygous.

CO-DOMINANCE  – Is a situation where the phenotype of the heterozygote exhibits properties of both parents . Example of co-dominance is seen in ABO BLOOD GROUP SYSTEM IN HUMAN BLOOD GROUP a IS DOMINANT AS BLOOD  GROUP b. If a child is product by two parents, one with blood group B and the other blood group A. The child will belong to blood group AB.

SEX – LINKED CHARACTER – These are characters that are carried by genes located on the  sex chromosome . These genes or characters are said to be sex- linked and usually found in the  X- chromosome  they expressed in male children  even when  the gene is recessive . Such phenotype are expressed in female only when  the two X – chromosomes are recessive  or two x – chromosomes are recessive  or carry the recessive gene. Example of characteristics  expressed by genes that are located on sex chromosome include colour blindness,  hemophilia , baldness.

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