6.4 traits genes and alleles answer key
Model chromosomes are used by students to simulate the processes of meiosis and fertilization. Students follow the alleles of three human genes from the parents’ body cells from gametes to zygotes as they model meiosis and fertilization. Students will understand how genes are passed on from parents to children via the cycles of meiosis and fertilization in this way. To understand how meiosis and fertilization lead to genetic and phenotypic variation, students examine the effects of independent assortment, crossing over, and fertilization. Students also learn how to compare and contrast mitosis and meiosis, as well as how a mistake in meiosis can cause Down syndrome or embryo death. This practice can be used to implement or study the processes of meiosis and fertilization.
We also include a shorter Student Handout that omits the study of independent assortment, crossing over, and mistakes in meiosis, in addition to the more comprehensive Student Handout (described above). We estimate that the longer Student Handout will take about two 50-minute periods and the shorter Student Handout will take about 112 50-minute periods to complete. “Mitosis, Meiosis, and Fertilization–Major Concepts, Common Misconceptions, and Learning Activities” (available at http://serendip.brynmawr.edu/exchang…MitosisMeiosis) suggests some improvements.
Complex patterns of inheritance
The cell cycle, which allows life to continue from one cell to the next, is the basis of life continuity. The cell cycle is an ordered series of events that occurs in the life of a cell, starting with the division of a single parent cell to produce two new daughter cells and ending with the division of those daughter cells. The cell cycle processes are strongly conserved in all eukaryotes. Similar measures are used by species as diverse as protists, plants, and animals.
A clearer understanding of the structure and function of a cell’s genetic information is needed before discussing the steps a cell takes to replicate. The genome refers to a cell’s full collection of DNA. The genome of prokaryotes is made up of a single double-stranded DNA molecule shaped like a loop or circle. A nucleoid is the part of the cell that contains the genetic material. Some prokaryotes also have plasmids, which are smaller DNA loops that aren’t needed for normal development.
In eukaryotes, the genome is made up of many double-stranded, linear DNA molecules (Figure 6.2) that are bound together by proteins to form chromosomes. In the nuclei of each cell, each eukaryote species has a specific number of chromosomes. Somatic cells (body cells) in humans have 46 chromosomes. Diploid means that a somatic cell has two sets of chromosomes that are similar. A diploid organism is called 2n since the letter n is used to denote a single set of chromosomes. Gametes, or sex cells, are human cells with just one set of 23 chromosomes; these eggs and sperm are marked n, or haploid.
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Gregor Mendel, a Moravian scientist and Augustinian friar working in Brno in the 19th century, was the first to research genetics scientifically, despite the fact that heredity had been studied for millennia. Mendel looked at “trait inheritance,” or how traits are passed down from parents to children. He discovered that species (pea plants) inherit traits in distinct “inheritance units.” This term, which is still in use today, is an unclear description of what is known as a gene.
In the twenty-first century, trait inheritance and molecular inheritance mechanisms of genes are still primary concepts of genetics, but modern genetics has grown beyond inheritance to include the study of gene function and behavior. The structure and function of genes, as well as their variation and distribution, are studied in the sense of the cell, the organism (e.g. dominance), and a population. Molecular genetics, epigenetics, and population genetics are only a few of the subfields of genetics. The organisms studied in this wide area come from all walks of life (archaea, bacteria, and eukarya).
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Mendel founded the basis of genetics.
Punnett squares 101
Traits are inherited distinguishing traits. (e.g., eye and hair color) The study of biological inheritance patterns and variation is known as genetics. Traits are inherited as discrete units, according to Gregor Mendel. Like a jumble of various colored marbles that can still be picked out separately.
Per gene receives one allele from each parent.
Any alternate type of a gene found at a particular locus on a chromosome is referred to as an allele. (alleles=wrinkled or smooth, gene=pea shape) Per gene receives one allele from each parent. -Genotype: A particular set of genes’ genetic makeup. -Phenotype: An individual’s physical features – what you really SEE – At a particular locus, homozygous(purebred) identifies two alleles that are identical. For instance: (RR or rr) At a particular locus, heterozygous (Hybrid) identifies two alleles that are distinct. For instance: (Rr)
Letters may be used to represent alleles.
When at least one allele is dominant, it expresses itself as a phenotype (visible trait). Only when two copies of a recessive allele are present does it manifest as a phenotype (visible trait). Uppercase letters represent dominant alleles, while lowercase letters represent recessive alleles.