Structure and Function of Gene part I By

Structure and Function of Gene (part I) By Estri Laras Arumingtyas Fatchiyah Irfan Mustafa

Gregor Mendel n n n One of the pioneers in genetics Used scientific approach to understand genetic features: • Character: is a heritable feature like flower color • Trait: Traits: Each variant for a character Gregor Mendel in 1857 started to experiment with: • Pea Plants

Character Dominant traits Recessive traits

1857 Experiment

To explain his results, Mendel formulated a hypothesis that included the following: 1. In the organism there is a pair of “factors” that controls the appearance of a given characteristic. (We call them genes. ) 2. The organism inherits these “factors” from its parents, one from each. 3. Each is transmitted from generation to generation as a discrete, unchanging unit. (The wrinkled seeds in the F 2 generation were no less wrinkled than those in the P generation although they had passed through the round-seeded F 1 generation. ) 4. When the gametes are formed, the “factors” separate and are distributed as units to each gamete. This statement is often called Mendel's rule of segregation. 5. If an organism has two unlike factors (we call them alleles) for a characteristic, one may be expressed to the total exclusion of the other (dominant vs recessive).

Mendel’s principle of Segregation n Pairs of alleles segregate (separate) during gamete formation; the fusion of gametes at fertilization creates allele pairs again Ex: Tt organism • Each gamete gets either T or t, but not both

Mendel did not stop here… n n He went on to cross pea varieties that differed in six other qualitative traits. In every case, the results supported his hypothesis. He crossed peas that differed in two traits. He found that the inheritance of one trait was independent of that of the other and so framed his second rule: the rule of independent assortment.

Mendel’s principle of Independent Assortment n n By then doing an F 1 cross (Rr. Yy x Rr. Yy) Mendel showed that the allele for yellow (Y) didn’t always end up in the same gamete with the allele for round (R) Genes for different traits can segregate independently during the formation of gametes

Animal Inheritance

Human Inheritance

Mendel’s Model n n Alternative versions of genes account for variation in inherited characters • Alleles are alternative versions • Chromosome Gene Locus For each character, an individual inherits 2 alleles (P 1 and P 2): Two alleles being different have dominant or recessive alleles Dominant allele is expressed

Structure and Function of Gene (part II) By Estri Laras Arumingtyas Fatchiyah Irfan Mustafa

What is Inheritance? n n Passing on genetic information from parents to offspring Humans have 23 pairs of chromosomes (46 total) • 1 of each pair is from one parent and the other is from the other parent

Chromosomes n n n Chromosomes, threadlike structures, first observed by Nageli in 1842. Long strands of DNA that carry the genetic information on building and sustaining a living human being. Each chromosome contains many genes

What is a Gene? n A segment of a chromosome that containing the code for a single protein (enzyme) - The enzyme causes a chemical reaction that allows a trait to be expressed. ie. Production of a pigment n Something that stated by Mendel as “factor”

Round vs Wrinkled n n Dominant allele round codes for enzyme that converts sugar starch Recessive allele have defective enzyme • • • Sugar accumulates Water diffuses in the seed Seeds swell Mature seed when dried becomes wrinkled One dominant allele produces enough enzyme Both homozygous dominants and heterozygotes produce enough enzyme

Alleles n Alleles are alternate forms of a gene • Homozygous individuals have two identical alleles for a trait ex. : AA or aa organism • Heterozygous individuals have two different alleles for a trait ex. : Aa organism

Cell, chromosome and gene (DNA) The body contains trillions of cells chromatin Nucleus (center of cell) contains chromosomes and genes Chromosomes are threadlike structures composed of DNA molecules A gene, a segment of DNA (spiraled double chain) containing the hereditary code

The Structure of Chromosome n n Nucleotides --> DNA --> Gene --> Chromosome Human DNA is ~ 2 meters long. The nucleus of DNA is about 6 µM in diameter. So, how the very long DNA is packed into a very small nucleus?

Chromosome Structure fatchiyah, JB UB

Type of chromosome structure Metacentric Submetacentric Acrocentric Chrom. 1 Chrom. 9 Chrom. 14 The ideogram is basically a "chromosome map" showing the relationship between the short and long arms, centromere (cen). The specific banding patterns are also illustrated. Each band is numbered to aid in describing rearrangements. 1. The short arm is designated as p and the long arm as q. 2. The centromere is the location of spindle attachment and is an integral part of the chromosome. 3. It is essential for the normal movement and segregation of chromosomes during cell division.

What molecule transmitting genetic inheritance from parents to offspring ? DNA (Deoxyribose Nucleic Acid)

THE STRUCTURE OF DNA

DNA: terminology base sugar nucleoside base phosphate(s) sugar nucleotides (nucleoside mono-, di-, and triphosphates)

DNA: structure 1. 2. 3. 4. 5. 6. 7. 8. 9. DNA is double stranded DNA strands are antiparallel G-C pairs have 3 hydrogen bonds A-T pairs have 2 hydrogen bonds One strand is the complement of the other Major and minor grooves present different surfaces 7. Almost all cellular DNA is B-DNA 8. B-DNA has ~10. 5 bp/turn of the helix

Gene expression in eucaryotes and procaryotes

Molecular Definition of Gene n n The entire nucleic acid sequence that is necessary for the synthesis of a functional protein and RNA Coding region (exon and intron) + Regulatory sequences (e. g. promoter=the site where RNA polymerase binds prior to the initiation of transcription)

Basic Gene Structures n Eukaryotic genes • Exons, introns, • translation starts and stops, splice (donor/acceptor) junctions

Basic Gene Structure n Prokaryotic genes • coding regions, non-coding regions • translation starts and stops promoter gene start gene stop Prokaryotic genes are easier to identify than eukaryotic genes because of the simplicity of their gene structure and the density of genes in the genome