The World of Genetics by: brooke Tran

This here is Gregor Mendel, "Father of Genetics", breeder of pea plants, and the first to study heredity.

Gregor Mendel bred pea plants in order to study the traits that were passed along to their offspring, what is known as heredity. He noticed that within the new generation there were traits or genes that hadn’t been there before.

This was due to the fact that a gene is composed of two alleles, one from each parent. The alleles are responsible for which traits show up in the next generation and are represented through letters, either a capitalized letter or lower case letter. A dominant allele being the one to always be expressed in offspring with an upper case letter and the lower case letter being a recessive allele which is only expressed when the dominant allele is absent. In the case of which you have a gene made up of two capital letters (BB) you have homozygous dominant, if its two lower case letters (bb) it’s homozygous recessive and if you have one of each (Bb) then it’s heterozygous gene the dominant allele will still show through however, covering up the recessive trait this is known as Mendel’s Principle of Dominance where the recessive gene will make a reappearance in future generations.

Using a Punnett square you can determine the probability of traits for offspring. A Punnett square is made up of four entire squares with each of the parent’s two alleles bordering the top of the squares and the left side.

Many of our traits are managed by multiple genes. That's why there are so many different variations in skin color, height, hair color, and so on. The reason it's possible for some of these traits to change over time is because of your epigenome. This allows for traits to be expressed and genetic information to be read easier.

The likelihood of a trait is determined through the amount of times it appears on the squares. Each square represents a 25% chance of the offspring inheriting that phenotype, so if black hair is a dominant trait and one of the parents' genes for this trait is homozygous dominant and the other is heterozygous than there is a 50% chance of the offspring being born with homozygous dominant black hair and 50% heterozygous dominant hair. Although, let it be known that even if the offspring do not display the genotype they can still inherit that trait and be a carrier, it may just reappear in another generation.

The varying colors stay separate and can be easily "spotted".

However it is possible for offspring to inherit and display both traits rather than just show the dominant trait. There are two different ways multiple phenotypes can be expressed, one being codominance and the other being incomplete dominance. For example, codominance can be represented by a dalmatian; with its black or brown spots standing out against its white coat.

The brown rabbit's blended fur is evident in the picture above.

Incomplete dominance is where the multiple phenotypes are expressed through a blend. A prime example would be if a rabbit with a red coat and a rabbit with a white coat were to produce offspring they’d have kits with brown fur as a result of one rabbit’s red allele and one rabbit’s white allele not dominating. This is because the different coat colors blended and produced an incomplete dominant phenotype.

"--not dominating."

An organism’s complete set of genes or genome can be found on chromosomes.

Chromosomes come in in pairs, one chromosome coming from each the mother and father. There is one certain pair that determines whether the organism will be male or female, these are called sex chromosomes. The remaining pairs within the genome are called autosomes.

There are specific diseases and disorders that can be passed down through autosomes and sex chromosomes. The physical expression of the trait depends on if it is dominant or recessive however, just like any other trait. Just like the other traits, it can only be seen when it is dominant, it doesn’t matter whether it’s homozygous dominant or heterozygous for the genotype because the dominant trait will always show and so only one of the alleles has to possess the trait. This is unlike with an autosomal recessive trait where two alleles have to be present, what is known as homozygous recessive genotype, in order for the trait to be seen by the eye. If an organism has only one of these alleles then it will not be shown through a phenotype since the dominant trait will conceal it. Although just like with any other trait it can still be passed along to their offspring, what is known as a carrier.

Sex chromosomes contain sex-linked traits, they vary and depending on if you're female (XX) or male (XY) carry different sex chromosome combination. Females are able to pass on an X chromosome while males can pass on either X or Y. This means that the male is what determines the sex of the offspring. Males cannot pass a trait onto females. Females do not contain a Y chromosome which are vulnerable to dominant genes since they do not have a recessive gene which would be found on the X chromosome. Although there are rare cases where she might inherit the trait and express it or she may just be a carrier.

Blood types can also be found using Punnet squares as well. There are four different blood types that exist within humans: A, B, Ab, or O. If you were to receive blood you'd have to know what your blood type so it is compatible with the blood that is being donated. The possible blood types someone may have are A+, A-, B+, B-, AB+, AB-, O+, or O-. Like with all genes there are two alleles, one from the mother and one from the father. You can also be be homozygous or heterozygous for blood typing.

A part of your blood is the Rhesus factor this is a protein that determines whether it's positive (+) or negative (-). Women need to make it a point to know what their Rh factor is if she intends on carrying a child. This is because if the fetus were to have a negative Rhesus factor and the mother were to have a positive one than the opposing factors endanger both the child and mother. With the mother's body rejecting the baby as a result, however, it's possible for the mother to bear a child with an opposite Rhesus factor if she were to take very strong medication throughout the pregnancy.

The 22 pairs are numbered, paired, and arranged.

A karyotype is an chromosomal profile of a person's chromosomes. Geneticists use the chromosomal alternations to identify what may result to be a genetic disorder, it lets parents know what disease or disorder they're at risk for and might pass along to their children. This can be done by drawing blood and analyzing the DNA, looking for chromosomes that may be defected.

The squares represent the females and the circles represent the males. The dark circles or squares show that that person contains the trait, while the shapes that are not filled represent those who are unaffected.

Pedigree is the recorded ancestry which can track the inheritance patterns for each generation. Only one trait can be shown at a time on one pedigree chart.


Created with images by ColiN00B - "dna dns biology"

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