This standard examines how DNA and chromosomes in inheritance work together to pass qualities from parents to children.

DNA and Chromosomes in Inheritance

Inheritance Overview

There has been convincing evidence that organisms acquire features from their parents since the days of Gregor Mendel (about 1850). Mendel, a monk and the inventor of genetics, researched the many features of pea plants and how they were handed down. Mendel discovered that a lot of features seemed to have many unique forms-what we now refer to as alleles. Mendel also recognised that certain alleles dominated others, as seen in the diagram below.

However, since Mendel’s pea plant trials, we’ve come a long way. Mendel’s Laws are now fully understood genetic pathways.

DNA and Chromosomes in Inheritance

DNA

DNA constructs proteins from the ground up. Proteins have a variety of roles in cells. This results in quantifiable characteristics such as eye colour and height (or flower colour in plants).

Mendel discovered alleles, which are genetic differences inside the DNA. Even though people share 99.9% of their DNA sequence, 0.1 percent of tiny nucleotide alterations, deletions, and insertions in the DNA code may radically alter the function of practically every protein. These alterations may be significant in certain cases, such as the total absence of protein function seen in many recessive disorders. Occasionally, a change in protein function may merely halt or speed up a process that is important for the creation of certain characteristics.

DNA and Chromosomes in Inheritance

Inheritance through DNA

When one gamete fertilises the other, a zygote is created (sperm and egg cells in many organisms). To make a diploid cell, each gamete cell contains one copy of the DNA code—you have two copies of the 23 chromosomes in each cell of your body.

Sexually reproducing creatures employ the meiosis process (seen below) to produce gametes (and covered further in other standards).

Several processes may happen during meiosis that lead to allele variation within a population. First, new mutations in DNA may develop during DNA replication or as a result of an environmental mutagen. These mutations may be passed on to progeny if they occur in a line of cells that generate gametes. Furthermore, genes for diverse qualities are randomly allocated to gametes during meiosis, and chromosomes may be altered. Because it recombines alleles from maternal and paternal lineages into novel combinations, this enhances organism variety.

DNA and Chromosomes in Inheritance

Investigating Inheritance

There are lots of animal and plant photographs available for students to perform their own genetic research, as well as many fantastic techniques to assist students examine the process of heredity. A few simple genetic tools can make a big difference. The Punnett square, as seen below, is perhaps the most beneficial tool.

Punnett squares may be used to forecast the children of a certain parental cross or to estimate the number of alleles present in a population. Fruit flies and pea plants offer a broad range of qualities that have been well-documented, but students may explore practically any creature they desire to understand the genetic inheritance patterns for this criterion.

What to Avoid

The following Assessment Boundary is also included in this NGSS standard:

The stages of meiosis or the biochemical mechanisms of individual steps in the process are not included in the evaluation.

Let’s take a closer look at these two lines:

Phases of Meiosis:

It is not required to analyse and model the stages of mitosis for this standard. Students should instead be evaluated on the larger topics underlying the function of meiosis in inheritance. Mendel’s Law of Segregation and the Law of Independent Assortment are created during meiosis because the chromosomes are messed up and some crossing-over occurs. Mendel’s Law of Dominance is based on protein function and the fact that a single functioning copy of a gene is frequently sufficient to produce a feature (such as purple flowers).

Biochemical Mechanisms:

The term “biochemical mechanism” in this case refers to both how certain processes in meiosis occur and how specific alleles result in a particular phenotypic variation.

In pea plants, for example, the purple-flower allele is a gene that creates a protein that is required for the formation of purple pigment molecules. The “purple allele” is dominant over the “white allele,” which needs two non-functional alleles and is recessive, since one functional allele provides enough purple pigment. Anything more biological, such as the process that the protein impacts or how the protein works, is beyond the scope of this standard.